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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 `1`

to `99999`

, `MEDIUMINT UNSIGNED`

is the best type. Of the types that represent all the required values, this type uses the least amount of storage.

Tables created in MySQL 5.0.3 and above uses a new storage format for `DECIMAL`

columns. All basic calculation (`+,-,*,/`

) with `DECIMAL`

columns are done with precision of 65 decimal (base 10) digits. See Section 11.1.1, “Overview of Numeric Types”.

Prior to MySQL 5.0.3, calculations on `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 a `BIGINT`

. This allows you to do all calculations with 64-bit integers and then convert results back to floating-point values as necessary.