Mysql 5.5 and 5.6 timestamp fields DEFAULT CURRENT_TIMESTAMP ON UPDA

This article will introduce the differences between mysql 5.5 and 5.6 timestamp fields DEFAULT CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP. I hope this tutorial will be helpful to you.

Mysql5.6 database:

The Code is as follows:

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[BIGHD] (root@127.0.0.1) [cm]> SELECT version (); + ------------ + | Version () | + ------------ + | 5.6.13-log | + ------------ + 1 row in set (0.02 sec)   [BIGHD] (root@127.0.0.1) [cm]> alter table s _ uk ADD 'last _ op_time 'timestamp not null default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP; Query OK, 0 ROWS affected (0.99 sec) Records: 0 Duplicates: 0 Warnings: 0   [BIGHD] (root@127.0.0.1) [cm]> SELECT id, last_op_time FROM s _ uk LIMIT 1; + ---- + --------------------- + | Id | last_op_time | + ---- + --------------------- + | 1 | 10:17:57 | + ---- + --------------------- + 1 row in set (0.00 sec)

 
 
Mysql5.5 database:

The Code is as follows:

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(Root @ localhost) [cm]> SELECT version (); + ------------ + | Version () | + ------------ + | 5.5.15-log | + ------------ + 1 row in set (0.00 sec)   (Root @ localhost) [cm]> alter table s _ uk ADD 'last _ op_time 'timestamp not null default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP; Query OK, 2523 ROWS affected (0.99 sec) Records: 2523 Duplicates: 0 Warnings: 0   (Root @ localhost) [cm]> SELECT last_op_time FROM s _ uk LIMIT 1; + --------------------- + | Last_op_time | + --------------------- + | 0000-00-00 00:00:00 | + --------------------- + 1 row in set (0.00 sec)

In addition, have you considered how to update this field? Will it be the specified time or the automatic generation time?

The Code is as follows:

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(Root @ localhost) [cm]> UPDATE s _ uk SET last_op_time = '2017-12-12 00:00:00 'WHERE id = 1; Query OK, 1 ROW affected (0.07 sec) ROWS matched: 1 Changed: 1 Warnings: 0   (Root @ localhost) [cm]> SELECT id, last_op_time FROM s _ uk LIMIT 1; + ---- + --------------------- + | Id | last_op_time | + ---- + --------------------- + | 1 | 00:00:00 | + ---- + --------------------- + 1 row in set (0.01 sec)

Right?

PS:
How can I determine whether a field contains multi-byte characters (such as Chinese )?

CHARACTER_LENGTH (value) = length (value) does not contain multi-byte characters.

Length is the byte length, and CHARACTER_LENGTH is the character characters length.

PS2:
Mongodb find ()

The function for subsequent beautification/formatting output is:
Db. tbl. find (). pretty ()