Recording a Row's Last Modification Time : TimeStamp « Data Type « SQL / MySQL






  1. SQL / MySQL
  2. Data Type
  3. TimeStamp

Recording a Row's Last Modification Time

      
mysql>
mysql> CREATE TABLE tsdemo1
    -> (
    -> t TIMESTAMP,
    -> val INT
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> INSERT INTO tsdemo1 (t,val) VALUES(NULL,5);
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO tsdemo1 (val) VALUES(10);
Query OK, 1 row affected (0.00 sec)

mysql>  SELECT * FROM tsdemo1;
+---------------------+------+
| t                   | val  |
+---------------------+------+
| 2011-10-03 13:05:52 |    5 |
| 2011-10-03 13:05:52 |   10 |
+---------------------+------+
2 rows in set (0.00 sec)

mysql>
mysql> UPDATE tsdemo1 SET val = 6 WHERE val = 5;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM tsdemo1;
+---------------------+------+
| t                   | val  |
+---------------------+------+
| 2011-10-03 13:05:52 |    6 |
| 2011-10-03 13:05:52 |   10 |
+---------------------+------+
2 rows in set (0.00 sec)

mysql>
mysql> drop table tsdemo1;
Query OK, 0 rows affected (0.00 sec)








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6.Recording a Row's Creation Time
7.Performing Calculations with TIMESTAMP Values
8.Updates to tsdemo2 records that don't actually modify a column cause no change to TIMESTAMP values
9.Create a table in which timestamps can be stored.
10.The difference between the creation and modification times
11.Issuing an UPDATE statement that doesn't actually change the values in the val column doesn't update the TIMES
12.microseconds component is removed.