The format is 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or numeric context.
SYSDATE() returns the time at which it executes.
NOW() returns a constant time that indicates the time at which the statement began to execute.
The SET TIMESTAMP statement affects the value returned by NOW() but not by SYSDATE().
mysql>
mysql> SELECT NOW(), SLEEP(2), NOW();
+---------------------+----------+---------------------+
| NOW() | SLEEP(2) | NOW() |
+---------------------+----------+---------------------+
| 2007-07-22 19:46:18 | 0 | 2007-07-22 19:46:18 |
+---------------------+----------+---------------------+
1 row in set (2.00 sec)
mysql>
mysql> SELECT SYSDATE(), SLEEP(2), SYSDATE();
+---------------------+----------+---------------------+
| SYSDATE() | SLEEP(2) | SYSDATE() |
+---------------------+----------+---------------------+
| 2007-07-22 19:46:20 | 0 | 2007-07-22 19:46:22 |
+---------------------+----------+---------------------+
1 row in set (2.00 sec)
mysql>
mysql>