MySQL — SQLAlchemy 1.0 Documentation

Release: 1.0.14 | Release Date: July 6, 2016

# SQLAlchemy 1.0 Documentation

# MySQL

Support for the MySQL database.

## DBAPI Support

The following dialect/DBAPI options are available. Please refer to individual DBAPI sections for connect information.

- MySQL-Python
- PyMySQL
- MySQL Connector/Python
- CyMySQL
- OurSQL
- Google Cloud SQL
- PyODBC
- zxjdbc for Jython

## Supported Versions and Features

SQLAlchemy supports MySQL starting with version 4.1 through modern releases. However, no heroic measures are taken to work around major missing SQL features - if your server version does not support sub-selects, for example, they won’t work in SQLAlchemy either.

See the official MySQL documentation for detailed information about features supported in any given server release.

## Connection Timeouts

MySQL features an automatic connection close behavior, for connections that have been idle for eight hours or more. To circumvent having this issue, use the `pool_recycle` option which controls the maximum age of any connection:

    engine = create_engine('mysql+mysqldb://...', pool_recycle=3600)

See also

Setting Pool Recycle - full description of the pool recycle feature.

## CREATE TABLE arguments including Storage Engines

MySQL’s CREATE TABLE syntax includes a wide array of special options, including `ENGINE`, `CHARSET`, `MAX_ROWS`, `ROW_FORMAT`, `INSERT_METHOD`, and many more. To accommodate the rendering of these arguments, specify the form `mysql_argument_name="value"`. For example, to specify a table with `ENGINE` of `InnoDB`, `CHARSET` of `utf8`, and `KEY_BLOCK_SIZE` of `1024`:

    Table('mytable', metadata,
          Column('data', String(32)),
          mysql_engine='InnoDB',
          mysql_charset='utf8',
          mysql_key_block_size="1024"
         )

The MySQL dialect will normally transfer any keyword specified as `mysql_keyword_name` to be rendered as `KEYWORD_NAME` in the `CREATE TABLE` statement. A handful of these names will render with a space instead of an underscore; to support this, the MySQL dialect has awareness of these particular names, which include `DATA DIRECTORY` (e.g. `mysql_data_directory`), `CHARACTER SET` (e.g. `mysql_character_set`) and `INDEX DIRECTORY` (e.g. `mysql_index_directory`).

The most common argument is `mysql_engine`, which refers to the storage engine for the table. Historically, MySQL server installations would default to `MyISAM` for this value, although newer versions may be defaulting to `InnoDB`. The `InnoDB` engine is typically preferred for its support of transactions and foreign keys.

A `Table` that is created in a MySQL database with a storage engine of `MyISAM` will be essentially non-transactional, meaning any INSERT/UPDATE/DELETE statement referring to this table will be invoked as autocommit. It also will have no support for foreign key constraints; while the `CREATE TABLE` statement accepts foreign key options, when using the `MyISAM` storage engine these arguments are discarded. Reflecting such a table will also produce no foreign key constraint information.

For fully atomic transactions as well as support for foreign key constraints, all participating `CREATE TABLE` statements must specify a transactional engine, which in the vast majority of cases is `InnoDB`.

See also

The InnoDB Storage Engine - on the MySQL website.

## Case Sensitivity and Table Reflection

MySQL has inconsistent support for case-sensitive identifier names, basing support on specific details of the underlying operating system. However, it has been observed that no matter what case sensitivity behavior is present, the names of tables in foreign key declarations are always received from the database as all-lower case, making it impossible to accurately reflect a schema where inter-related tables use mixed-case identifier names.

Therefore it is strongly advised that table names be declared as all lower case both within SQLAlchemy as well as on the MySQL database itself, especially if database reflection features are to be used.

## Transaction Isolation Level

All MySQL dialects support setting of transaction isolation level both via a dialect-specific parameter `create_engine.isolation_level` accepted by `create_engine()`, as well as the `Connection.execution_options.isolation_level` argument as passed to `Connection.execution_options()`. This feature works by issuing the command `SET SESSION TRANSACTION ISOLATION LEVEL <level>` for each new connection.

To set isolation level using `create_engine()`:

    engine = create_engine(
                    "mysql://scott:tiger@localhost/test",
                    isolation_level="READ UNCOMMITTED"
                )

To set using per-connection execution options:

    connection = engine.connect()
    connection = connection.execution_options(
        isolation_level="READ COMMITTED"
    )

Valid values for `isolation_level` include:

- `READ COMMITTED`
- `READ UNCOMMITTED`
- `REPEATABLE READ`
- `SERIALIZABLE`

## AUTO_INCREMENT Behavior

When creating tables, SQLAlchemy will automatically set `AUTO_INCREMENT` on the first `Integer` primary key column which is not marked as a foreign key:

    >>> t = Table('mytable', metadata,
    ...   Column('mytable_id', Integer, primary_key=True)
    ... )
    >>> t.create()
    CREATE TABLE mytable (
            id INTEGER NOT NULL AUTO_INCREMENT,
            PRIMARY KEY (id)
    )

You can disable this behavior by passing `False` to the `autoincrement` argument of `Column`. This flag can also be used to enable auto-increment on a secondary column in a multi-column key for some storage engines:

    Table('mytable', metadata,
          Column('gid', Integer, primary_key=True, autoincrement=False),
          Column('id', Integer, primary_key=True)
         )

## Unicode

### Charset Selection

Most MySQL DBAPIs offer the option to set the client character set for a connection. This is typically delivered using the `charset` parameter in the URL, such as:

    e = create_engine("mysql+pymysql://scott:tiger@localhost/test?charset=utf8")

This charset is the client character set for the connection. Some MySQL DBAPIs will default this to a value such as `latin1`, and some will make use of the `default-character-set` setting in the `my.cnf` file as well. Documentation for the DBAPI in use should be consulted for specific behavior.

The encoding used for Unicode has traditionally been `'utf8'`. However, for MySQL versions 5.5.3 on forward, a new MySQL-specific encoding `'utf8mb4'` has been introduced. The rationale for this new encoding is due to the fact that MySQL’s utf-8 encoding only supports codepoints up to three bytes instead of four. Therefore, when communicating with a MySQL database that includes codepoints more than three bytes in size, this new charset is preferred, if supported by both the database as well as the client DBAPI, as in:

    e = create_engine("mysql+pymysql://scott:tiger@localhost/test?charset=utf8mb4")

At the moment, up-to-date versions of MySQLdb and PyMySQL support the `utf8mb4` charset. Other DBAPIs such as MySQL-Connector and OurSQL may not support it as of yet.

In order to use `utf8mb4` encoding, changes to the MySQL schema and/or server configuration may be required.

See also

The utf8mb4 Character Set - in the MySQL documentation

### Unicode Encoding / Decoding

All modern MySQL DBAPIs all offer the service of handling the encoding and decoding of unicode data between the Python application space and the database. As this was not always the case, SQLAlchemy also includes a comprehensive system of performing the encode/decode task as well. As only one of these systems should be in use at at time, SQLAlchemy has long included functionality to automatically detect upon first connection whether or not the DBAPI is automatically handling unicode.

Whether or not the MySQL DBAPI will handle encoding can usually be configured using a DBAPI flag `use_unicode`, which is known to be supported at least by MySQLdb, PyMySQL, and MySQL-Connector. Setting this value to `0` in the “connect args” or query string will have the effect of disabling the DBAPI’s handling of unicode, such that it instead will return data of the `str` type or `bytes` type, with data in the configured charset:

    # connect while disabling the DBAPI's unicode encoding/decoding
    e = create_engine("mysql+mysqldb://scott:tiger@localhost/test?charset=utf8&use_unicode=0")

Current recommendations for modern DBAPIs are as follows:

- It is generally always safe to leave the `use_unicode` flag set at its default; that is, don’t use it at all.
- Under Python 3, the `use_unicode=0` flag should never be used. SQLAlchemy under Python 3 generally assumes the DBAPI receives and returns string values as Python 3 strings, which are inherently unicode objects.
- Under Python 2 with MySQLdb, the `use_unicode=0` flag will offer superior performance, as MySQLdb’s unicode converters under Python 2 only have been observed to have unusually slow performance compared to SQLAlchemy’s fast C-based encoders/decoders.

In short: don’t specify `use_unicode` at all, with the possible exception of `use_unicode=0` on MySQLdb with Python 2 only for a potential performance gain.

## Ansi Quoting Style

MySQL features two varieties of identifier “quoting style”, one using backticks and the other using quotes, e.g. ``some_identifier`` vs. `"some_identifier"`. All MySQL dialects detect which version is in use by checking the value of `sql_mode` when a connection is first established with a particular `Engine`. This quoting style comes into play when rendering table and column names as well as when reflecting existing database structures. The detection is entirely automatic and no special configuration is needed to use either quoting style.

Changed in version 0.6: detection of ANSI quoting style is entirely automatic, there’s no longer any end-user `create_engine()` options in this regard.

## MySQL SQL Extensions

Many of the MySQL SQL extensions are handled through SQLAlchemy’s generic function and operator support:

    table.select(table.c.password==func.md5('plaintext'))
    table.select(table.c.username.op('regexp')('^[a-d]'))

And of course any valid MySQL statement can be executed as a string as well.

Some limited direct support for MySQL extensions to SQL is currently available.

- SELECT pragma:

      select(..., prefixes=['HIGH_PRIORITY', 'SQL_SMALL_RESULT'])

- UPDATE with LIMIT:

      update(..., mysql_limit=10)

## rowcount Support

SQLAlchemy standardizes the DBAPI `cursor.rowcount` attribute to be the usual definition of “number of rows matched by an UPDATE or DELETE” statement. This is in contradiction to the default setting on most MySQL DBAPI drivers, which is “number of rows actually modified/deleted”. For this reason, the SQLAlchemy MySQL dialects always add the `constants.CLIENT.FOUND_ROWS` flag, or whatever is equivalent for the target dialect, upon connection. This setting is currently hardcoded.

See also

`ResultProxy.rowcount`

## CAST Support

MySQL documents the CAST operator as available in version 4.0.2. When using the SQLAlchemy `cast()` function, SQLAlchemy will not render the CAST token on MySQL before this version, based on server version detection, instead rendering the internal expression directly.

CAST may still not be desirable on an early MySQL version post-4.0.2, as it didn’t add all datatype support until 4.1.1. If your application falls into this narrow area, the behavior of CAST can be controlled using the Custom SQL Constructs and Compilation Extension system, as per the recipe below:

    from sqlalchemy.sql.expression import Cast
    from sqlalchemy.ext.compiler import compiles

    @compiles(Cast, 'mysql')
    def _check_mysql_version(element, compiler, **kw):
        if compiler.dialect.server_version_info < (4, 1, 0):
            return compiler.process(element.clause, **kw)
        else:
            return compiler.visit_cast(element, **kw)

The above function, which only needs to be declared once within an application, overrides the compilation of the `cast()` construct to check for version 4.1.0 before fully rendering CAST; else the internal element of the construct is rendered directly.

## MySQL Specific Index Options

MySQL-specific extensions to the `Index` construct are available.

### Index Length

MySQL provides an option to create index entries with a certain length, where “length” refers to the number of characters or bytes in each value which will become part of the index. SQLAlchemy provides this feature via the `mysql_length` parameter:

    Index('my_index', my_table.c.data, mysql_length=10)

    Index('a_b_idx', my_table.c.a, my_table.c.b, mysql_length={'a': 4,
                                                               'b': 9})

Prefix lengths are given in characters for nonbinary string types and in bytes for binary string types. The value passed to the keyword argument must be either an integer (and, thus, specify the same prefix length value for all columns of the index) or a dict in which keys are column names and values are prefix length values for corresponding columns. MySQL only allows a length for a column of an index if it is for a CHAR, VARCHAR, TEXT, BINARY, VARBINARY and BLOB.

New in version 0.8.2: `mysql_length` may now be specified as a dictionary for use with composite indexes.

### Index Types

Some MySQL storage engines permit you to specify an index type when creating an index or primary key constraint. SQLAlchemy provides this feature via the `mysql_using` parameter on `Index`:

    Index('my_index', my_table.c.data, mysql_using='hash')

As well as the `mysql_using` parameter on `PrimaryKeyConstraint`:

    PrimaryKeyConstraint("data", mysql_using='hash')

The value passed to the keyword argument will be simply passed through to the underlying CREATE INDEX or PRIMARY KEY clause, so it must be a valid index type for your MySQL storage engine.

More information can be found at:

http://dev.mysql.com/doc/refman/5.0/en/create-index.html

http://dev.mysql.com/doc/refman/5.0/en/create-table.html

## MySQL Foreign Keys

MySQL’s behavior regarding foreign keys has some important caveats.

### Foreign Key Arguments to Avoid

MySQL does not support the foreign key arguments “DEFERRABLE”, “INITIALLY”, or “MATCH”. Using the `deferrable` or `initially` keyword argument with `ForeignKeyConstraint` or `ForeignKey` will have the effect of these keywords being rendered in a DDL expression, which will then raise an error on MySQL. In order to use these keywords on a foreign key while having them ignored on a MySQL backend, use a custom compile rule:

    from sqlalchemy.ext.compiler import compiles
    from sqlalchemy.schema import ForeignKeyConstraint

    @compiles(ForeignKeyConstraint, "mysql")
    def process(element, compiler, **kw):
        element.deferrable = element.initially = None
        return compiler.visit_foreign_key_constraint(element, **kw)

Changed in version 0.9.0: - the MySQL backend no longer silently ignores the `deferrable` or `initially` keyword arguments of `ForeignKeyConstraint` and `ForeignKey`.

The “MATCH” keyword is in fact more insidious, and is explicitly disallowed by SQLAlchemy in conjunction with the MySQL backend. This argument is silently ignored by MySQL, but in addition has the effect of ON UPDATE and ON DELETE options also being ignored by the backend. Therefore MATCH should never be used with the MySQL backend; as is the case with DEFERRABLE and INITIALLY, custom compilation rules can be used to correct a MySQL ForeignKeyConstraint at DDL definition time.

New in version 0.9.0: - the MySQL backend will raise a `CompileError` when the `match` keyword is used with `ForeignKeyConstraint` or `ForeignKey`.

### Reflection of Foreign Key Constraints

Not all MySQL storage engines support foreign keys. When using the very common `MyISAM` MySQL storage engine, the information loaded by table reflection will not include foreign keys. For these tables, you may supply a `ForeignKeyConstraint` at reflection time:

    Table('mytable', metadata,
          ForeignKeyConstraint(['other_id'], ['othertable.other_id']),
          autoload=True
         )

See also

CREATE TABLE arguments including Storage Engines

## MySQL Unique Constraints and Reflection

SQLAlchemy supports both the `Index` construct with the flag `unique=True`, indicating a UNIQUE index, as well as the `UniqueConstraint` construct, representing a UNIQUE constraint. Both objects/syntaxes are supported by MySQL when emitting DDL to create these constraints. However, MySQL does not have a unique constraint construct that is separate from a unique index; that is, the “UNIQUE” constraint on MySQL is equivalent to creating a “UNIQUE INDEX”.

When reflecting these constructs, the `Inspector.get_indexes()` and the `Inspector.get_unique_constraints()` methods will both return an entry for a UNIQUE index in MySQL. However, when performing full table reflection using `Table(..., autoload=True)`, the `UniqueConstraint` construct is not part of the fully reflected `Table` construct under any circumstances; this construct is always represented by a `Index` with the `unique=True` setting present in the `Table.indexes` collection.

## TIMESTAMP Columns and NULL

MySQL historically enforces that a column which specifies the TIMESTAMP datatype implicitly includes a default value of CURRENT_TIMESTAMP, even though this is not stated, and additionally sets the column as NOT NULL, the opposite behavior vs. that of all other datatypes:

    mysql> CREATE TABLE ts_test (
        -> a INTEGER,
        -> b INTEGER NOT NULL,
        -> c TIMESTAMP,
        -> d TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        -> e TIMESTAMP NULL);
    Query OK, 0 rows affected (0.03 sec)

    mysql> SHOW CREATE TABLE ts_test;
    +---------+-----------------------------------------------------
    | Table   | Create Table
    +---------+-----------------------------------------------------
    | ts_test | CREATE TABLE `ts_test` (
      `a` int(11) DEFAULT NULL,
      `b` int(11) NOT NULL,
      `c` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
      `d` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
      `e` timestamp NULL DEFAULT NULL
    ) ENGINE=MyISAM DEFAULT CHARSET=latin1

Above, we see that an INTEGER column defaults to NULL, unless it is specified with NOT NULL. But when the column is of type TIMESTAMP, an implicit default of CURRENT_TIMESTAMP is generated which also coerces the column to be a NOT NULL, even though we did not specify it as such.

This behavior of MySQL can be changed on the MySQL side using the explicit_defaults_for_timestamp configuration flag introduced in MySQL 5.6. With this server setting enabled, TIMESTAMP columns behave like any other datatype on the MySQL side with regards to defaults and nullability.

However, to accommodate the vast majority of MySQL databases that do not specify this new flag, SQLAlchemy emits the “NULL” specifier explicitly with any TIMESTAMP column that does not specify `nullable=False`. In order to accommodate newer databases that specify `explicit_defaults_for_timestamp`, SQLAlchemy also emits NOT NULL for TIMESTAMP columns that do specify `nullable=False`. The following example illustrates:

    from sqlalchemy import MetaData, Integer, Table, Column, text
    from sqlalchemy.dialects.mysql import TIMESTAMP

    m = MetaData()
    t = Table('ts_test', m,
            Column('a', Integer),
            Column('b', Integer, nullable=False),
            Column('c', TIMESTAMP),
            Column('d', TIMESTAMP, nullable=False)
        )

    from sqlalchemy import create_engine
    e = create_engine("mysql://scott:tiger@localhost/test", echo=True)
    m.create_all(e)

output:

    CREATE TABLE ts_test (
        a INTEGER,
        b INTEGER NOT NULL,
        c TIMESTAMP NULL,
        d TIMESTAMP NOT NULL
    )

Changed in version 1.0.0: - SQLAlchemy now renders NULL or NOT NULL in all cases for TIMESTAMP columns, to accommodate `explicit_defaults_for_timestamp`. Prior to this version, it will not render “NOT NULL” for a TIMESTAMP column that is `nullable=False`.

## MySQL Data Types

As with all SQLAlchemy dialects, all UPPERCASE types that are known to be valid with MySQL are importable from the top level dialect:

    from sqlalchemy.dialects.mysql import \
            BIGINT, BINARY, BIT, BLOB, BOOLEAN, CHAR, DATE, \
            DATETIME, DECIMAL, DECIMAL, DOUBLE, ENUM, FLOAT, INTEGER, \
            LONGBLOB, LONGTEXT, MEDIUMBLOB, MEDIUMINT, MEDIUMTEXT, NCHAR, \
            NUMERIC, NVARCHAR, REAL, SET, SMALLINT, TEXT, TIME, TIMESTAMP, \
            TINYBLOB, TINYINT, TINYTEXT, VARBINARY, VARCHAR, YEAR

Types which are specific to MySQL, or have MySQL-specific construction arguments, are as follows:

class `sqlalchemy.dialects.mysql.` `BIGINT`(display_width=None, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._IntegerType`, `sqlalchemy.types.BIGINT`

  MySQL BIGINTEGER type.

  `__init__`(display_width=None, **kw)

    Construct a BIGINTEGER.

    Parameters: | display_width – Optional, maximum display width for this number. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `BINARY`(length=None)

  Bases: `sqlalchemy.types._Binary`

  The SQL BINARY type.

class `sqlalchemy.dialects.mysql.` `BIT`(length=None)

  Bases: `sqlalchemy.types.TypeEngine`

  MySQL BIT type.

  This type is for MySQL 5.0.3 or greater for MyISAM, and 5.0.5 or greater for MyISAM, MEMORY, InnoDB and BDB. For older versions, use a MSTinyInteger() type.

  `__init__`(length=None)

    Construct a BIT.

    Parameters: | length – Optional, number of bits.

class `sqlalchemy.dialects.mysql.` `BLOB`(length=None)

  Bases: `sqlalchemy.types.LargeBinary`

  The SQL BLOB type.

  `__init__`(length=None)
    inherited from the `__init__()` method of `LargeBinary`

    Construct a LargeBinary type.

    Parameters: | length – optional, a length for the column for use in DDL statements, for those binary types that accept a length, such as the MySQL BLOB type.

class `sqlalchemy.dialects.mysql.` `BOOLEAN`(create_constraint=True, name=None, _create_events=True)

  Bases: `sqlalchemy.types.Boolean`

  The SQL BOOLEAN type.

  `__init__`(create_constraint=True, name=None, _create_events=True)
    inherited from the `__init__()` method of `Boolean`

    Construct a Boolean.

    Parameters: | create_constraint – defaults to True. If the boolean is generated as an int/smallint, also create a CHECK constraint on the table that ensures 1 or 0 as a value. name – if a CHECK constraint is generated, specify the name of the constraint.

class `sqlalchemy.dialects.mysql.` `CHAR`(length=None, **kwargs)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`, `sqlalchemy.types.CHAR`

  MySQL CHAR type, for fixed-length character data.

  `__init__`(length=None, **kwargs)

    Construct a CHAR.

    Parameters: | length – Maximum data length, in characters. binary – Optional, use the default binary collation for the national character set. This does not affect the type of data stored, use a BINARY type for binary data. collation – Optional, request a particular collation. Must be compatible with the national character set.

class `sqlalchemy.dialects.mysql.` `DATE`

  Bases: `sqlalchemy.types.Date`

  The SQL DATE type.

  `__init__`
    inherited from the `__init__` attribute of `object`

    x.__init__(...) initializes x; see help(type(x)) for signature

class `sqlalchemy.dialects.mysql.` `DATETIME`(timezone=False, fsp=None)

  Bases: `sqlalchemy.types.DATETIME`

  MySQL DATETIME type.

  `__init__`(timezone=False, fsp=None)

    Construct a MySQL DATETIME type.

    Parameters: | timezone – not used by the MySQL dialect. fsp – fractional seconds precision value. MySQL 5.6.4 supports storage of fractional seconds; this parameter will be used when emitting DDL for the DATETIME type. Note DBAPI driver support for fractional seconds may be limited; current support includes MySQL Connector/Python.

    New in version 0.8.5: Added MySQL-specific `mysql.DATETIME` with fractional seconds support.

class `sqlalchemy.dialects.mysql.` `DECIMAL`(precision=None, scale=None, asdecimal=True, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._NumericType`, `sqlalchemy.types.DECIMAL`

  MySQL DECIMAL type.

  `__init__`(precision=None, scale=None, asdecimal=True, **kw)

    Construct a DECIMAL.

    Parameters: | precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server. scale – The number of digits after the decimal point. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `DOUBLE`(precision=None, scale=None, asdecimal=True, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._FloatType`

  MySQL DOUBLE type.

  `__init__`(precision=None, scale=None, asdecimal=True, **kw)

    Construct a DOUBLE.

    Note

    The `DOUBLE` type by default converts from float to Decimal, using a truncation that defaults to 10 digits. Specify either `scale=n` or `decimal_return_scale=n` in order to change this scale, or `asdecimal=False` to return values directly as Python floating points.

    Parameters: | precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server. scale – The number of digits after the decimal point. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `ENUM`(*enums, **kw)

  Bases: `sqlalchemy.types.Enum`, `sqlalchemy.dialects.mysql.base._EnumeratedValues`

  MySQL ENUM type.

  `__init__`(*enums, **kw)

    Construct an ENUM.

    E.g.:

        Column('myenum', ENUM("foo", "bar", "baz"))

    Parameters: | enums – The range of valid values for this ENUM. Values will be quoted when generating the schema according to the quoting flag (see below). strict – Defaults to False: ensure that a given value is in this ENUM’s range of permissible values when inserting or updating rows. Note that MySQL will not raise a fatal error if you attempt to store an out of range value- an alternate value will be stored instead. (See MySQL ENUM documentation.) charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand. collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand. ascii – Defaults to False: short-hand for the `latin1` character set, generates ASCII in schema. unicode – Defaults to False: short-hand for the `ucs2` character set, generates UNICODE in schema. binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data. quoting – Defaults to ‘auto’: automatically determine enum value quoting. If all enum values are surrounded by the same quoting character, then use ‘quoted’ mode. Otherwise, use ‘unquoted’ mode. ‘quoted’: values in enums are already quoted, they will be used directly when generating the schema - this usage is deprecated. ‘unquoted’: values in enums are not quoted, they will be escaped and surrounded by single quotes when generating the schema. Previous versions of this type always required manually quoted values to be supplied; future versions will always quote the string literals for you. This is a transitional option.

class `sqlalchemy.dialects.mysql.` `FLOAT`(precision=None, scale=None, asdecimal=False, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._FloatType`, `sqlalchemy.types.FLOAT`

  MySQL FLOAT type.

  `__init__`(precision=None, scale=None, asdecimal=False, **kw)

    Construct a FLOAT.

    Parameters: | precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server. scale – The number of digits after the decimal point. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `INTEGER`(display_width=None, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._IntegerType`, `sqlalchemy.types.INTEGER`

  MySQL INTEGER type.

  `__init__`(display_width=None, **kw)

    Construct an INTEGER.

    Parameters: | display_width – Optional, maximum display width for this number. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `LONGBLOB`(length=None)

  Bases: `sqlalchemy.types._Binary`

  MySQL LONGBLOB type, for binary data up to 2^32 bytes.

class `sqlalchemy.dialects.mysql.` `LONGTEXT`(**kwargs)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`

  MySQL LONGTEXT type, for text up to 2^32 characters.

  `__init__`(**kwargs)

    Construct a LONGTEXT.

    Parameters: | charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand. collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand. ascii – Defaults to False: short-hand for the `latin1` character set, generates ASCII in schema. unicode – Defaults to False: short-hand for the `ucs2` character set, generates UNICODE in schema. national – Optional. If true, use the server’s configured national character set. binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class `sqlalchemy.dialects.mysql.` `MEDIUMBLOB`(length=None)

  Bases: `sqlalchemy.types._Binary`

  MySQL MEDIUMBLOB type, for binary data up to 2^24 bytes.

class `sqlalchemy.dialects.mysql.` `MEDIUMINT`(display_width=None, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._IntegerType`

  MySQL MEDIUMINTEGER type.

  `__init__`(display_width=None, **kw)

    Construct a MEDIUMINTEGER

    Parameters: | display_width – Optional, maximum display width for this number. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `MEDIUMTEXT`(**kwargs)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`

  MySQL MEDIUMTEXT type, for text up to 2^24 characters.

  `__init__`(**kwargs)

    Construct a MEDIUMTEXT.

    Parameters: | charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand. collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand. ascii – Defaults to False: short-hand for the `latin1` character set, generates ASCII in schema. unicode – Defaults to False: short-hand for the `ucs2` character set, generates UNICODE in schema. national – Optional. If true, use the server’s configured national character set. binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class `sqlalchemy.dialects.mysql.` `NCHAR`(length=None, **kwargs)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`, `sqlalchemy.types.NCHAR`

  MySQL NCHAR type.

  For fixed-length character data in the server’s configured national character set.

  `__init__`(length=None, **kwargs)

    Construct an NCHAR.

    Parameters: | length – Maximum data length, in characters. binary – Optional, use the default binary collation for the national character set. This does not affect the type of data stored, use a BINARY type for binary data. collation – Optional, request a particular collation. Must be compatible with the national character set.

class `sqlalchemy.dialects.mysql.` `NUMERIC`(precision=None, scale=None, asdecimal=True, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._NumericType`, `sqlalchemy.types.NUMERIC`

  MySQL NUMERIC type.

  `__init__`(precision=None, scale=None, asdecimal=True, **kw)

    Construct a NUMERIC.

    Parameters: | precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server. scale – The number of digits after the decimal point. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `NVARCHAR`(length=None, **kwargs)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`, `sqlalchemy.types.NVARCHAR`

  MySQL NVARCHAR type.

  For variable-length character data in the server’s configured national character set.

  `__init__`(length=None, **kwargs)

    Construct an NVARCHAR.

    Parameters: | length – Maximum data length, in characters. binary – Optional, use the default binary collation for the national character set. This does not affect the type of data stored, use a BINARY type for binary data. collation – Optional, request a particular collation. Must be compatible with the national character set.

class `sqlalchemy.dialects.mysql.` `REAL`(precision=None, scale=None, asdecimal=True, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._FloatType`, `sqlalchemy.types.REAL`

  MySQL REAL type.

  `__init__`(precision=None, scale=None, asdecimal=True, **kw)

    Construct a REAL.

    Note

    The `REAL` type by default converts from float to Decimal, using a truncation that defaults to 10 digits. Specify either `scale=n` or `decimal_return_scale=n` in order to change this scale, or `asdecimal=False` to return values directly as Python floating points.

    Parameters: | precision – Total digits in this number. If scale and precision are both None, values are stored to limits allowed by the server. scale – The number of digits after the decimal point. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `SET`(*values, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._EnumeratedValues`

  MySQL SET type.

  `__init__`(*values, **kw)

    Construct a SET.

    E.g.:

        Column('myset', SET("foo", "bar", "baz"))

    The list of potential values is required in the case that this set will be used to generate DDL for a table, or if the `SET.retrieve_as_bitwise` flag is set to True.

    Parameters: | values – The range of valid values for this SET. convert_unicode – Same flag as that of `String.convert_unicode`. collation – same as that of `String.collation` charset – same as that of `VARCHAR.charset`. ascii – same as that of `VARCHAR.ascii`. unicode – same as that of `VARCHAR.unicode`. binary – same as that of `VARCHAR.binary`. quoting – Defaults to ‘auto’: automatically determine set value quoting. If all values are surrounded by the same quoting character, then use ‘quoted’ mode. Otherwise, use ‘unquoted’ mode. ‘quoted’: values in enums are already quoted, they will be used directly when generating the schema - this usage is deprecated. ‘unquoted’: values in enums are not quoted, they will be escaped and surrounded by single quotes when generating the schema. Previous versions of this type always required manually quoted values to be supplied; future versions will always quote the string literals for you. This is a transitional option. New in version 0.9.0. retrieve_as_bitwise – if True, the data for the set type will be persisted and selected using an integer value, where a set is coerced into a bitwise mask for persistence. MySQL allows this mode which has the advantage of being able to store values unambiguously, such as the blank string `''`. The datatype will appear as the expression `col + 0` in a SELECT statement, so that the value is coerced into an integer value in result sets. This flag is required if one wishes to persist a set that can store the blank string `''` as a value. Warning When using `mysql.SET.retrieve_as_bitwise`, it is essential that the list of set values is expressed in the exact same order as exists on the MySQL database. New in version 1.0.0.

class `sqlalchemy.dialects.mysql.` `SMALLINT`(display_width=None, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._IntegerType`, `sqlalchemy.types.SMALLINT`

  MySQL SMALLINTEGER type.

  `__init__`(display_width=None, **kw)

    Construct a SMALLINTEGER.

    Parameters: | display_width – Optional, maximum display width for this number. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `TEXT`(length=None, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`, `sqlalchemy.types.TEXT`

  MySQL TEXT type, for text up to 2^16 characters.

  `__init__`(length=None, **kw)

    Construct a TEXT.

    Parameters: | length – Optional, if provided the server may optimize storage by substituting the smallest TEXT type sufficient to store `length` characters. charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand. collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand. ascii – Defaults to False: short-hand for the `latin1` character set, generates ASCII in schema. unicode – Defaults to False: short-hand for the `ucs2` character set, generates UNICODE in schema. national – Optional. If true, use the server’s configured national character set. binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class `sqlalchemy.dialects.mysql.` `TIME`(timezone=False, fsp=None)

  Bases: `sqlalchemy.types.TIME`

  MySQL TIME type.

  `__init__`(timezone=False, fsp=None)

    Construct a MySQL TIME type.

    Parameters: | timezone – not used by the MySQL dialect. fsp – fractional seconds precision value. MySQL 5.6 supports storage of fractional seconds; this parameter will be used when emitting DDL for the TIME type. Note DBAPI driver support for fractional seconds may be limited; current support includes MySQL Connector/Python.

    New in version 0.8: The MySQL-specific TIME type as well as fractional seconds support.

class `sqlalchemy.dialects.mysql.` `TIMESTAMP`(timezone=False, fsp=None)

  Bases: `sqlalchemy.types.TIMESTAMP`

  MySQL TIMESTAMP type.

  `__init__`(timezone=False, fsp=None)

    Construct a MySQL TIMESTAMP type.

    Parameters: | timezone – not used by the MySQL dialect. fsp – fractional seconds precision value. MySQL 5.6.4 supports storage of fractional seconds; this parameter will be used when emitting DDL for the TIMESTAMP type. Note DBAPI driver support for fractional seconds may be limited; current support includes MySQL Connector/Python.

    New in version 0.8.5: Added MySQL-specific `mysql.TIMESTAMP` with fractional seconds support.

class `sqlalchemy.dialects.mysql.` `TINYBLOB`(length=None)

  Bases: `sqlalchemy.types._Binary`

  MySQL TINYBLOB type, for binary data up to 2^8 bytes.

class `sqlalchemy.dialects.mysql.` `TINYINT`(display_width=None, **kw)

  Bases: `sqlalchemy.dialects.mysql.base._IntegerType`

  MySQL TINYINT type.

  `__init__`(display_width=None, **kw)

    Construct a TINYINT.

    Parameters: | display_width – Optional, maximum display width for this number. unsigned – a boolean, optional. zerofill – Optional. If true, values will be stored as strings left-padded with zeros. Note that this does not effect the values returned by the underlying database API, which continue to be numeric.

class `sqlalchemy.dialects.mysql.` `TINYTEXT`(**kwargs)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`

  MySQL TINYTEXT type, for text up to 2^8 characters.

  `__init__`(**kwargs)

    Construct a TINYTEXT.

    Parameters: | charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand. collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand. ascii – Defaults to False: short-hand for the `latin1` character set, generates ASCII in schema. unicode – Defaults to False: short-hand for the `ucs2` character set, generates UNICODE in schema. national – Optional. If true, use the server’s configured national character set. binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class `sqlalchemy.dialects.mysql.` `VARBINARY`(length=None)

  Bases: `sqlalchemy.types._Binary`

  The SQL VARBINARY type.

class `sqlalchemy.dialects.mysql.` `VARCHAR`(length=None, **kwargs)

  Bases: `sqlalchemy.dialects.mysql.base._StringType`, `sqlalchemy.types.VARCHAR`

  MySQL VARCHAR type, for variable-length character data.

  `__init__`(length=None, **kwargs)

    Construct a VARCHAR.

    Parameters: | charset – Optional, a column-level character set for this string value. Takes precedence to ‘ascii’ or ‘unicode’ short-hand. collation – Optional, a column-level collation for this string value. Takes precedence to ‘binary’ short-hand. ascii – Defaults to False: short-hand for the `latin1` character set, generates ASCII in schema. unicode – Defaults to False: short-hand for the `ucs2` character set, generates UNICODE in schema. national – Optional. If true, use the server’s configured national character set. binary – Defaults to False: short-hand, pick the binary collation type that matches the column’s character set. Generates BINARY in schema. This does not affect the type of data stored, only the collation of character data.

class `sqlalchemy.dialects.mysql.` `YEAR`(display_width=None)

  Bases: `sqlalchemy.types.TypeEngine`

  MySQL YEAR type, for single byte storage of years 1901-2155.

## MySQL-Python

Support for the MySQL database via the MySQL-Python driver.

### DBAPI

Documentation and download information (if applicable) for MySQL-Python is available at: http://sourceforge.net/projects/mysql-python

### Connecting

Connect String:

    mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>

### Unicode

Please see Unicode for current recommendations on unicode handling.

### Py3K Support

Currently, MySQLdb only runs on Python 2 and development has been stopped. mysqlclient is fork of MySQLdb and provides Python 3 support as well as some bugfixes.

### Using MySQLdb with Google Cloud SQL

Google Cloud SQL now recommends use of the MySQLdb dialect. Connect using a URL like the following:

    mysql+mysqldb://root@/<dbname>?unix_socket=/cloudsql/<projectid>:<instancename>

## pymysql

Support for the MySQL database via the PyMySQL driver.

### DBAPI

Documentation and download information (if applicable) for PyMySQL is available at: http://www.pymysql.org/

### Connecting

Connect String:

    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]

### Unicode

Please see Unicode for current recommendations on unicode handling.

### MySQL-Python Compatibility

The pymysql DBAPI is a pure Python port of the MySQL-python (MySQLdb) driver, and targets 100% compatibility. Most behavioral notes for MySQL-python apply to the pymysql driver as well.

## MySQL-Connector

Support for the MySQL database via the MySQL Connector/Python driver.

### DBAPI

Documentation and download information (if applicable) for MySQL Connector/Python is available at: http://dev.mysql.com/downloads/connector/python/

### Connecting

Connect String:

    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>

### Unicode

Please see Unicode for current recommendations on unicode handling.

## cymysql

Support for the MySQL database via the CyMySQL driver.

### DBAPI

Documentation and download information (if applicable) for CyMySQL is available at: https://github.com/nakagami/CyMySQL

### Connecting

Connect String:

    mysql+cymysql://<username>:<password>@<host>/<dbname>[?<options>]

## OurSQL

Support for the MySQL database via the OurSQL driver.

### DBAPI

Documentation and download information (if applicable) for OurSQL is available at: http://packages.python.org/oursql/

### Connecting

Connect String:

    mysql+oursql://<user>:<password>@<host>[:<port>]/<dbname>

### Unicode

Please see Unicode for current recommendations on unicode handling.

## Google App Engine

Support for the MySQL database via the Google Cloud SQL driver.

This dialect is based primarily on the `mysql.mysqldb` dialect with minimal changes.

New in version 0.7.8.

Deprecated since version 1.0: This dialect is no longer necessary for Google Cloud SQL; the MySQLdb dialect can be used directly. Cloud SQL now recommends creating connections via the mysql dialect using the URL format

`mysql+mysqldb://root@/<dbname>?unix_socket=/cloudsql/<projectid>:<instancename>`

### DBAPI

Documentation and download information (if applicable) for Google Cloud SQL is available at: https://developers.google.com/appengine/docs/python/cloud-sql/developers-guide

### Connecting

Connect String:

    mysql+gaerdbms:///<dbname>?instance=<instancename>

### Pooling

Google App Engine connections appear to be randomly recycled, so the dialect does not pool connections. The `NullPool` implementation is installed within the `Engine` by default.

## pyodbc

Support for the MySQL database via the PyODBC driver.

Note

The PyODBC for MySQL dialect is not well supported, and is subject to unresolved character encoding issues which exist within the current ODBC drivers available. (see http://code.google.com/p/pyodbc/issues/detail?id=25). Other dialects for MySQL are recommended.

### DBAPI

Documentation and download information (if applicable) for PyODBC is available at: http://pypi.python.org/pypi/pyodbc/

### Connecting

Connect String:

    mysql+pyodbc://<username>:<password>@<dsnname>

## zxjdbc

Support for the MySQL database via the zxjdbc for Jython driver.

Note

Jython is not supported by current versions of SQLAlchemy. The zxjdbc dialect should be considered as experimental.

### DBAPI

Drivers for this database are available at: http://dev.mysql.com/downloads/connector/j/

### Connecting

Connect String:

    mysql+zxjdbc://<user>:<password>@<hostname>[:<port>]/<database>

### Character Sets

SQLAlchemy zxjdbc dialects pass unicode straight through to the zxjdbc/JDBC layer. To allow multiple character sets to be sent from the MySQL Connector/J JDBC driver, by default SQLAlchemy sets its `characterEncoding` connection property to `UTF-8`. It may be overridden via a `create_engine` URL parameter.