FLOAT[(M,D)] [UNSIGNED] [ZEROFILL]

A small (single-precision) floating-point number. Permissible values
are -3.402823466E+38 to -1.175494351E-38, 0, and 1.175494351E-38 to
3.402823466E+38. These are the theoretical limits, based on the IEEE
standard. The actual range might be slightly smaller depending on your
hardware or operating system.

M is the total number of digits and D is the number of digits following
the decimal point. If M and D are omitted, values are stored to the
limits permitted by the hardware. A single-precision floating-point
number is accurate to approximately 7 decimal places.

UNSIGNED, if specified, disallows negative values.

Using FLOAT might give you some unexpected problems because all
calculations in MySQL are done with double precision. See
http://dev.mysql.com/doc/refman/5.0/en/no-matching-rows.html.

URL: http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html

