MYSQL 类型转换函数 CAST

CONVERT(

expr

,

type

)

,

CONVERT(

expr

USING

transcoding_name

)

The

CONVERT()

and

CAST()

functions take a value of one type and produce a value of another type.

The

type

can be one of the following values:

• BINARY[(

  N

  )]

• CHAR[(

  N

  )]

• DATE

• DATETIME

• DECIMAL[(

  M

  [,

  D

  ])]

• SIGNED [INTEGER]

• TIME

• UNSIGNED [INTEGER]

http://dev.mysql.com/doc/refman/5.0/en/cast-functions.html#function_convert