Automatic generation and update of timestamp in MySQL

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The timestamp type in MySQL can set default values, just like any other type.
1, Automatic Update and insert to the current time:
Table:
---------------------------------
Table Create Table
------ --------------------------

CREATE TABLE ' T1 ' (  


  

Data:

1 2007-10-08 11:53:35
2 2007-10-08 11:54:00

INSERT into T1 (p_c) Select 3;
Update T1 Set P_c = 2 where p_c = 2;

Data:

1 2007-10-08 11:53:35
2 2007-10-08 12:00:37
3 2007-10-08 12:00:37

2, automatic insert to the current time, but does not automatically update.

Table:
---------------------------------
Table Create Table
------ ---------------------------

CREATE TABLE ' T1 ' (  

Data:

INSERT into T1 (p_c) Select 4;
Update T1 Set P_c = 3 where p_c = 3;

1 2007-10-08 11:53:35
2 2007-10-08 12:00:37
3 2007-10-08 12:00:37
4 2007-10-08 12:05:19


3. Cannot have two fields in a table the default value is the current time, otherwise an error occurs. But the others can.
Table:
---------------------------------
Table Create Table
------ --------------------------

CREATE TABLE ' T1 ' (  

Data:
1 2007-10-08 11:53:35 0000-00-00 00:00:00
2 2007-10-08 12:00:37 0000-00-00 00:00:00
3 2007-10-08 12:00:37 0000-00-00 00:00:00
4 2007-10-08 12:05:19 0000-00-00 00:00:00

Automatic generation and update of timestamp in MySQL