Difference between MySQL 5.5 and 5.6 timestamp field DEFAULT current_timestamp on UPDATE current_timestamp

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 CURR Ent_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 | 2013-10-10 10:17:57 | +----+---------------------+ 1 ROW in SET (0.00 sec)

mysql5.5 Database:

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)

Also, have you ever considered what would happen if you only updated this field? Will it be the time specified, or is it automatically generated?

The code is as follows	Copy Code
(root@localhost) [cm]> UPDATE s__uk SET last_op_time= ' 2012-12-12 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 | 2012-12-12 00:00:00 | +----+---------------------+ 1 ROW in SET (0.01 sec)

Guess what, wood?

Ps:
How do I determine if there are multibyte characters in a field (such as Chinese)?

Character_length (value) = LENGTH (value) does not contain multibyte characters.

Length is the byte bytes length, Character_length is the character characters length.

PS2:
MongoDB Find ()

Then the function of beautifying/formatting the output is:
Db.tbl.find (). Pretty ()