TIMESTAMP indicates when each row in the table was last modified. When a column is declared with DEFAULT TIMESTAMP, a default value is provided for inserts, and the value is updated with the current date and time whenever the row is updated.
TIMESTAMP
Columns declared with DEFAULT TIMESTAMP contain unique values so that applications can detect near-simultaneous updates to the same row. If the current timestamp value is the same as the last value, it is incremented by the value of the default_timestamp_increment option.
You can automatically truncate timestamp values in SQL Anywhere based on the default_timestamp_increment option. This is useful for maintaining compatibility with other database software that records less precise timestamp values.
The global variable @@dbts returns a TIMESTAMP value representing the last value generated for a column using DEFAULT TIMESTAMP
Data type
TIMESTAMP
Remarks
Columns declared with DEFAULT TIMESTAMP contain unique values so that applications can detect near-simultaneous updates to the same row. If the current timestamp value is the same as the last value, it is incremented by the value of the default_timestamp_increment option.
You can automatically truncate timestamp values in SQL Anywhere based on the default_timestamp_increment option. This is useful for maintaining compatibility with other database software that records less precise timestamp values.
The global variable @@dbts returns a TIMESTAMP value representing the last value generated for a column using DEFAULT TIMESTAMP
The main difference between DEFAULT TIMESTAMP and DEFAULT CURRENT TIMESTAMP is that DEFAULT CURRENT TIMESTAMP is set only at INSERT, while DEFAULT TIMESTAMP is set at both INSERT and UPDATE.
没有评论:
发表评论