79476

Data types. These data type changes have been implemented:

•    MySQL now permits fractional seconds for TIME, datetime, and TIMESTAMP values, with upto

microseconds (6 digits) precision. See Section 11.3.6, “Fractional Seconds in Time Values”.

•    Previously, at most one timestamp column per table could be automatically initialized or

updated to the current datę and time. This restriction has been lifted. Any TIMESTAMP column

definition can have any combination of default current timestamp and ON UPDATE

current_timestamp clauses. In addition, these clauses now can be used with datetime

column definitions. For morę information, see Section 11.3.5, “Automatic Initialization and

Updating for timestamp and DATETIME”.

•    In MySQL, the TIMESTAMP data type differs in nonstandard ways from other data types in

terms of default value and assignment of automatic initialization and update attributes. These

behaviors remain the default but now are deprecated, and can be turned off by enabling the

explicit_def aults_for_timestamp [495] system variable at server startup. See

Section 11.3.5, “Automatic Initialization and Updating for timestamp and DATETIME”, and

Section 5.1.4, “Server System Variables”.

•    The year (2) data type is now deprecated. year (2) columns in existing tables are treated as

before, but year(2) in newor altered tables are converted to year(4). For morę information,

see Section 11.3.4, “year(2) Limitations and Migrating to YEAR(4)”.