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MySQL in a Nutshell by Russell J.T. Dyer

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Numeric Datatypes

Standard SQL numeric datatypes are allowed: accurate numeric (i.e., BIGINT, DECIMAL, INTEGER, MEDIUMINT, NUMERIC, SMALLINT, and TINYINT) and approximate numeric datatypes (i.e., DOUBLE PRECISION, FLOAT, and REAL).

For all numeric datatypes, you can use the UNSIGNED and ZEROFILL flags depending on your needs. If UNSIGNED is omitted, SIGNED is assumed. A numeric datatype has different allowable ranges based on whether it’s SIGNED or UNSIGNED. The ZEROFILL flag instructs MySQL to pad the unused spaces to the left of a number with spaces. For example, a column with a datatype set to INT(10) will display the number 5 as 0000000005. If the ZEROFILL flag is used, UNSIGNED is assumed for the column. When subtracting values where one is UNSIGNED, the results will become UNSIGNED.

For several of the numeric datatypes, a width for displaying may be specified. This cannot exceed 255. The display width is a factor only when ZEROFILL is used for the column. You may also specify the number of digits allowed for the decimals, including the decimal point.

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