11.6. Choosing the Right Type for a Column
For optimum storage, you should try to use the most precise type
in all cases. For example, if an integer column is used for values
in the range from
MEDIUMINT UNSIGNED is
the best type. Of the types that represent all the required
values, this type uses the least amount of storage.
All basic calculations (
DECIMAL columns are done with precision of 65
decimal (base 10) digits. See
Section 11.1.1, “Overview of Numeric Types”.
DECIMAL values are performed
using double-precision operations. If accuracy is not too
important or if speed is the highest priority, the
DOUBLE type may be good enough. For high
precision, you can always convert to a fixed-point type stored in
BIGINT. This allows you to do all
calculations with 64-bit integers and then convert results back to
floating-point values as necessary.