SQLAlchemy 0.4 Documentation - module sqlalchemy.databases.mysql

# SQLAlchemy 0.4 Documentation

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Version: 0.4.6 Last Updated: 05/14/08 14:36:43

### module sqlalchemy.databases.mysql

Support for the MySQL database.

SQLAlchemy supports 6 major MySQL versions: 3.23, 4.0, 4.1, 5.0, 5.1 and 6.0, with capablities increasing with more modern servers.

Versions 4.1 and higher support the basic SQL functionality that SQLAlchemy uses in the ORM and SQL expressions. These versions pass the applicable tests in the suite 100%. 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.

Currently, the only DB-API driver supported is MySQL-Python (also referred to as MySQLdb). Either 1.2.1 or 1.2.2 are recommended. The alpha, beta and gamma releases of 1.2.1 and 1.2.2 should be avoided. Support for Jython and IronPython is planned.

Feature | Minimum Version
--- | ---
sqlalchemy.orm | 4.1.1
Table Reflection | 3.23.x
DDL Generation | 4.1.1
utf8/Full Unicode Connections | 4.1.1
Transactions | 3.23.15
Two-Phase Transactions | 5.0.3
Nested Transactions | 5.0.3

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

Many MySQL server installations default to a `latin1` encoding for client connections. All data sent through the connection will be converted into `latin1`, even if you have `utf8` or another character set on your tables and columns. With versions 4.1 and higher, you can change the connection character set either through server configuration or by passing the `charset` parameter to `create_engine`. The `charset` option is passed through to MySQL-Python and has the side-effect of also enabling `use_unicode` in the driver by default. For regular encoded strings, also pass `use_unicode=0` in the connection arguments.

Most MySQL server installations have a default table type of MyISAM, a non-transactional table type. During a transaction, non-transactional storage engines do not participate and continue to store table changes in autocommit mode. For fully atomic transactions, all participating tables must use a transactional engine such as InnoDB, Falcon, SolidDB, PBXT, etc. Storage engines can be elected when creating tables in SQLAlchemy by supplying a `mysql_engine='whatever'` to the `Table` constructor. Any MySQL table creation option can be specified in this syntax.

Not all MySQL storage engines support foreign keys. For MyISAM and similar engines, the information loaded by table reflection will not include foreign keys. For these tables, you may supply `ForeignKeyConstraints` at reflection time:

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

When creating tables, SQLAlchemy will automatically set AUTO_INCREMENT on an integer primary key column:

    >>> 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 supplying `autoincrement=False` in addition. This 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))

MySQL SQL modes are supported. Modes that enable `ANSI_QUOTES` (such as `ANSI`) require an engine option to modify SQLAlchemy's quoting style. When using an ANSI-quoting mode, supply `use_ansiquotes=True` when creating your `Engine`:

    create_engine('mysql://localhost/test', use_ansiquotes=True)

This is an engine-wide option and is not toggleable on a per-connection basis. SQLAlchemy does not presume to `SET sql_mode` for you with this option. For the best performance, set the quoting style server-wide in `my.cnf` or by supplying `--sql-mode` to `mysqld`. You can also use a `Pool` hook to issue a `SET SESSION sql_mode='...'` on connect to configure each connection.

If you do not specify 'use_ansiquotes', the regular MySQL quoting style is used by default. Table reflection operations will query the server

If you do issue a 'SET sql_mode' through SQLAlchemy, the dialect must be updated if the quoting style is changed. Again, this change will affect all connections:

    connection.execute('SET sql_mode="ansi"')
    connection.dialect.use_ansiquotes = True

For normal SQLAlchemy usage, loading this module is unnescesary. It will be loaded on-demand when a MySQL connection is needed. The generic column types like `String` and `Integer` will automatically be adapted to the optimal matching MySQL column type.

But if you would like to use one of the MySQL-specific or enhanced column types when creating tables with your `Table` definitions, then you will need to import them from this module:

    from sqlalchemy.databases import mysql

    Table('mytable', metadata,
          Column('id', Integer, primary_key=True),
          Column('ittybittyblob', mysql.MSTinyBlob),
          Column('biggy', mysql.MSBigInteger(unsigned=True)))

All standard MySQL column types are supported. The OpenGIS types are available for use via table reflection but have no special support or mapping to Python classes. If you're using these types and have opinions about how OpenGIS can be smartly integrated into SQLAlchemy please join the mailing list!

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 statement can be executed as a string rather than through the SQL expression language.

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

> - SELECT pragma:

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

> - UPDATE with LIMIT:

>       update(..., mysql_limit=10)

If you have problems that seem server related, first check that you are using the most recent stable MySQL-Python package available. The Database Notes page on the wiki at http://www.sqlalchemy.org is a good resource for timely information affecting MySQL in SQLAlchemy.

### class MSBigInteger(MSInteger)

MySQL BIGINTEGER type.

def __init__(self, length=None, **kw)

Construct a BIGINTEGER.

length
  Optional, maximum display width for this number.
unsigned
  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.

def get_col_spec(self)
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### class MSBinary(_BinaryType)

MySQL BINARY type, for fixed length binary data

def __init__(self, length=None, **kw)

Construct a BINARY. This is a fixed length type, and short values will be right-padded with a server-version-specific pad value.

length
  Maximum data length, in bytes. If length is not specified, this will generate a BLOB. This usage is deprecated.

def get_col_spec(self)
def result_processor(self, dialect)
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### class MSBit(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(1) type.

def __init__(self, length=None)

Construct a new `MSBit`.

def get_col_spec(self)
def result_processor(self, dialect)

Convert a MySQL's 64 bit, variable length binary string to a long.

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### class MSBlob(_BinaryType)

MySQL BLOB type, for binary data up to 2^16 bytes

def __init__(self, length=None, **kw)

Construct a BLOB. Arguments are:

length
  Optional, if provided the server may optimize storage by subsitituting the smallest TEXT type sufficient to store `length` characters.

def get_col_spec(self)
def result_processor(self, dialect)
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### class MSBoolean(Boolean)

MySQL BOOLEAN type.

def bind_processor(self, dialect)
def get_col_spec(self)
def result_processor(self, dialect)
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### class MSChar(_StringType,CHAR)

MySQL CHAR type, for fixed-length character data.

def __init__(self, length, **kwargs)

Construct an NCHAR.

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 compatibile with the national character set.

def get_col_spec(self)
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### class MSDate(Date)

MySQL DATE type.

def get_col_spec(self)
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### class MSDateTime(DateTime)

MySQL DATETIME type.

def get_col_spec(self)
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### class MSDecimal(MSNumeric)

MySQL DECIMAL type.

def __init__(self, precision=10, length=2, asdecimal=True, **kw)

Construct a DECIMAL.

precision
  Total digits in this number. If length and precision are both None, values are stored to limits allowed by the server.
length
  The number of digits after the decimal point.
unsigned
  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.

def get_col_spec(self)
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### class MSDouble(Float,_NumericType)

MySQL DOUBLE type.

def __init__(self, precision=None, length=None, asdecimal=True, **kw)

Construct a DOUBLE.

precision
  Total digits in this number. If length and precision are both None, values are stored to limits allowed by the server.
length
  The number of digits after the decimal point.
unsigned
  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.

def get_col_spec(self)
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### class MSEnum(MSString)

MySQL ENUM type.

def __init__(self, *enums, **kw)

Construct an ENUM.

Example:

> Column('myenum', MSEnum("'foo'", "'bar'", "'baz'"))

Arguments are:

enums
  The range of valid values for this ENUM. Values will be used exactly as they appear when generating schemas. Strings must be quoted, as in the example above. Single-quotes are suggested for ANSI compatability and are required for portability to servers with ANSI_QUOTES enabled.
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 precendence 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.

def bind_processor(self, dialect)
def get_col_spec(self)
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### class MSFloat(Float,_NumericType)

MySQL FLOAT type.

def __init__(self, precision=None, length=None, asdecimal=False, **kw)

Construct a FLOAT.

precision
  Total digits in this number. If length and precision are both None, values are stored to limits allowed by the server.
length
  The number of digits after the decimal point.
unsigned
  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.

def bind_processor(self, dialect)
def get_col_spec(self)
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### class MSInteger(Integer,_NumericType)

MySQL INTEGER type.

def __init__(self, length=None, **kw)

Construct an INTEGER.

length
  Optional, maximum display width for this number.
unsigned
  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.

def get_col_spec(self)
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### class MSLongBlob(MSBlob)

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

def get_col_spec(self)
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### class MSLongText(MSText)

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

def __init__(self, **kwargs)

Construct a LONGTEXT.

charset
  Optional, a column-level character set for this string value. Takes precendence 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.

def get_col_spec(self)
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### class MSMediumBlob(MSBlob)

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

def get_col_spec(self)
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### class MSMediumText(MSText)

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

def __init__(self, **kwargs)

Construct a MEDIUMTEXT.

charset
  Optional, a column-level character set for this string value. Takes precendence 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.

def get_col_spec(self)
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### class MSNChar(_StringType,CHAR)

MySQL NCHAR type.

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

def __init__(self, length=None, **kwargs)

Construct an NCHAR. Arguments are:

length
  Maximum data length, in characters.
binary
  Optional, request the default binary collation for the national character set.
collation
  Optional, request a particular collation. Must be compatibile with the national character set.

def get_col_spec(self)
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### class MSNVarChar(_StringType,String)

MySQL NVARCHAR type.

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

def __init__(self, length=None, **kwargs)

Construct an NVARCHAR.

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 VARBINARY type for binary data.
collation
  Optional, request a particular collation. Must be compatibile with the national character set.

def get_col_spec(self)
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### class MSNumeric(Numeric,_NumericType)

MySQL NUMERIC type.

def __init__(self, precision=10, length=2, asdecimal=True, **kw)

Construct a NUMERIC.

precision
  Total digits in this number. If length and precision are both None, values are stored to limits allowed by the server.
length
  The number of digits after the decimal point.
unsigned
  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.

def bind_processor(self, dialect)
def get_col_spec(self)
def result_processor(self, dialect)
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### class MSSet(MSString)

MySQL SET type.

def __init__(self, *values, **kw)

Construct a SET.

Example:

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

Arguments are:

values
  The range of valid values for this SET. Values will be used exactly as they appear when generating schemas. Strings must be quoted, as in the example above. Single-quotes are suggested for ANSI compatability and are required for portability to servers with ANSI_QUOTES enabled.
charset
  Optional, a column-level character set for this string value. Takes precendence 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.

def bind_processor(self, dialect)
def get_col_spec(self)
def result_processor(self, dialect)
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### class MSSmallInteger(SmallInteger,MSInteger)

MySQL SMALLINTEGER type.

def __init__(self, length=None, **kw)

Construct a SMALLINTEGER.

length
  Optional, maximum display width for this number.
unsigned
  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.

def get_col_spec(self)
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### class MSString(_StringType,String)

MySQL VARCHAR type, for variable-length character data.

def __init__(self, length=None, **kwargs)

Construct a VARCHAR.

length
  Maximum data length, in characters.
charset
  Optional, a column-level character set for this string value. Takes precendence 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.

def get_col_spec(self)
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### class MSText(_StringType,Text)

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

def __init__(self, length=None, **kwargs)

Construct a TEXT.

length
  Optional, if provided the server may optimize storage by subsitituting the smallest TEXT type sufficient to store `length` characters.
charset
  Optional, a column-level character set for this string value. Takes precendence 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.

def get_col_spec(self)
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### class MSTime(Time)

MySQL TIME type.

def get_col_spec(self)
def result_processor(self, dialect)
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### class MSTimeStamp(TIMESTAMP)

MySQL TIMESTAMP type.

To signal the orm to automatically re-select modified rows to retrieve the updated timestamp, add a PassiveDefault to your column specification:

    from sqlalchemy.databases import mysql
    Column('updated', mysql.MSTimeStamp,
           PassiveDefault(sql.text('CURRENT_TIMESTAMP')))

The full range of MySQL 4.1+ TIMESTAMP defaults can be specified in the PassiveDefault:

    PassiveDefault(sql.text('CURRENT TIMESTAMP ON UPDATE CURRENT_TIMESTAMP'))

def get_col_spec(self)
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### class MSTinyBlob(MSBlob)

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

def get_col_spec(self)
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### class MSTinyInteger(MSInteger)

MySQL TINYINT type.

def __init__(self, length=None, **kw)

Construct a TINYINT.

Note: following the usual MySQL conventions, TINYINT(1) columns reflected during Table(..., autoload=True) are treated as Boolean columns.

length
  Optional, maximum display width for this number.
unsigned
  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.

def get_col_spec(self)
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### class MSTinyText(MSText)

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

def __init__(self, **kwargs)

Construct a TINYTEXT.

charset
  Optional, a column-level character set for this string value. Takes precendence 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.

def get_col_spec(self)
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### class MSVarBinary(_BinaryType)

MySQL VARBINARY type, for variable length binary data.

def __init__(self, length=None, **kw)

Construct a VARBINARY. Arguments are:

length
  Maximum data length, in bytes.

def get_col_spec(self)
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### class MSYear(TypeEngine)

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

def __init__(self, length=None)

Construct a new `MSYear`.

def get_col_spec(self)
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