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mysql 5.5与5.6 timestamp 字段 DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP的区别

2024-07-12 00:55:11   223人阅读

http://www.111cn.net/database/mysql/55392.htm

 

本文章来给各位同学介绍关于mysql 5.5与5.6 timestamp 字段 DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP的区别,希望此教程对各位有帮助。
 

mysql5.6数据库:

 代码如下复制代码
[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 | 2013-10-10 10:17:57 |
+----+---------------------+
1 ROW IN SET (0.00 sec)
 


 
 
mysql5.5数据库:

 代码如下复制代码

(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)

另外，有没有考虑过如果只更新这个字段会怎样？会是指定的时间，还是自动生成的时间？

 代码如下复制代码
(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)

猜对了木有？

PS:
如何判断字段中是否有多字节字符（比如中文）?

CHARACTER_LENGTH(value) = length(value) 则不包含多字节字符。

length为字节Bytes长度， CHARACTER_LENGTH为字符characters长度。

PS2:
mongodb find()

之后美化/格式化输出的函数是：
db.tbl.find().pretty()

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