Syntax:
CAST(expr AS type), CONVERT(expr,type), CONVERT(expr USING
transcoding_name)

The CAST() and CONVERT() functions take a value of one type and produce
a value of another type.

The type can be one of the following values:

o BINARY[(N)]

o CHAR[(N)]

o DATE

o DATETIME

o DECIMAL

o SIGNED [INTEGER]

o TIME

o UNSIGNED [INTEGER]

BINARY produces a string with the BINARY data type. See
http://dev.mysql.com/doc/refman/5.0/en/binary-varbinary.html for a
description of how this affects comparisons. If the optional length N
is given, BINARY(N) causes the cast to use no more than N bytes of the
argument. As of MySQL 5.0.17, values shorter than N bytes are padded
with 0x00 bytes to a length of N.

CHAR(N) causes the cast to use no more than N characters of the
argument.

The DECIMAL type is available as of MySQL 5.0.8.

CAST() and CONVERT(... USING ...) are standard SQL syntax. The
non-USING form of CONVERT() is ODBC syntax.

CONVERT() with USING is used to convert data between different
character sets. In MySQL, transcoding names are the same as the
corresponding character set names. For example, this statement converts
the string 'abc' in the default character set to the corresponding
string in the utf8 character set:

SELECT CONVERT('abc' USING utf8);

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

