本文实例讲述了mysql中的sql_mode模式。分享给大家供大家参考，具体如下：
mysql数据库的中有一个环境变量sql_mode,定义了mysql应该支持的sql语法，数据校验等！我们可以通过以下方式查看当前数据库使用的sql_mode：
mysql> select @@sql_mode; +----------------------------------------------------------------+ | @@sql_mode | +----------------------------------------------------------------+ | STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +----------------------------------------------------------------+
mysql5.0以上版本支持三种sql_mode模式
| ANSI模式 |
宽松模式，对插入数据进行校验，如果不符合定义类型或长度，对数据类型调整或截断保存，报warning警告。 |
| TRADITIONAL模式 |
严格模式，当向mysql数据库插入数据时，进行数据的严格校验，保证错误数据不能插入，报error错误。用于事物时，会进行事物的回滚。 |
| STRICT_TRANS_TABLES模式 |
严格模式，进行数据的严格校验，错误数据不能插入，报error错误。
|
1 ANSI模式
在ANSI模式下，当我们插入数据时，未满足列长度要求时，数据同样会插入成功，但是对超出列长度的字段进行截断，同时报告warning警告。
mysql> set @@sql_mode=ANSI;
Query OK, 0 rows affected (0.00 sec)
mysql> create table test(name varchar(4), pass varchar(4));
Query OK, 0 rows affected (0.03 sec)
mysql> insert into test values('aaaaa','aaaaa'),('bbbb','bbbb');
Query OK, 2 rows affected, 2 warnings (0.02 sec)
Records: 2 Duplicates: 0 Warnings: 2
mysql> show warnings;
+---------+------+-------------------------------------------+
| Level | Code | Message |
+---------+------+-------------------------------------------+
| Warning | 1265 | Data truncated for column 'name' at row 1 |
| Warning | 1265 | Data truncated for column 'pass' at row 1 |
+---------+------+-------------------------------------------+
2 rows in set (0.00 sec)
mysql> select * from test;
+------+------+
| name | pass |
+------+------+
| aaaa | aaaa |
| bbbb | bbbb |
+------+------+
2 rows in set (0.00 sec)
2 STRICT_TRANS_TABLES模式
在STRICT_TRANS_TABLES模式下，当我们插入数据时，mysql会严格的进行数据的校验，当发现插入列值未满足要求，直接报告error错误，保证了错误数据无法插入到数据库中。
mysql> set @@sql_mode=STRICT_TRANS_TABLES;
Query OK, 0 rows affected (0.00 sec)
mysql> create table test(name varchar(4), pass varchar(4));
Query OK, 0 rows affected (0.02 sec)
mysql> insert into test values('aaaaa','aaaaa'),('bbbb','bbbb');
ERROR 1406 (22001): Data too long for column 'name' at row 1
mysql> show errors;
+-------+------+------------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------------+
| Error | 1406 | Data too long for column 'name' at row 1 |
+-------+------+------------------------------------------+
1 row in set (0.00 sec)
mysql> select * from test;
Empty set (0.00 sec)
3 TRADITIONAL模式，初看结果是不是一样
mysql> set @@sql_mode=TRADITIONAL;
Query OK, 0 rows affected (0.00 sec)
mysql> create table test(name varchar(4), pass varchar(4));
Query OK, 0 rows affected (0.02 sec)
mysql> insert into test values('aaaaa','aaaaa'),('bbbb','bbbb');
ERROR 1406 (22001): Data too long for column 'name' at row 1
mysql> show errors;
+-------+------+------------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------------+
| Error | 1406 | Data too long for column 'name' at row 1 |
+-------+------+------------------------------------------+
1 row in set (0.00 sec)
mysql> select * from test;
Empty set (0.00 sec)
但是，可以看看设置后的情况
mysql> set @@sql_mode=TRADITIONAL; Query OK, 0 rows affected (0.00 sec) mysql> select @@sql_mode\G *************************** 1. row *************************** @@sql_mode: STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,TRADITIONAL,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION 1 row in set (0.00 sec)
在TRADITIONAL模式下，对所有的事务存储引擎，非事务存储引擎检查，日期类型中的月和日部分不能包含0，不能有0这样的日期(0000-00-00),数据不能除0，禁止grant自动创建新用户等一些校验。
最后：
set @@只是在sessions级别设置的，要想所有的都生效，还是要设置配置文件
vi /etc/my.cnf
在[mysqld]下面添加如下列：
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
#NO_ENGINE_SUBSTITUTION对于不存在的引擎就报错，不加的话，指定不支持的引擎时指定默认的innodb
另外：sql_mode还有一个配置ONLY_FULL_GROUP_BY，这个表示采用group by帅选数据的时候只能查看新组内信息
改模式之前的操作
mysql> select * from employee group by post; +----+--------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+--------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 | +----+--------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ 4 rows in set (0.00 sec)
此时的sql_mode:
mysql> select @@sql_mode; +----------------------------------------------------------------+ | @@sql_mode | +----------------------------------------------------------------+ | STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +----------------------------------------------------------------+ 1 row in set (0.00 sec)
修改一下，退出再进入才会生效
mysql> set global sql_mode='STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION,ONLY_FULL_GROUP_BY'; Query OK, 0 rows affected (0.00 sec) mysql> select @@sql_mode; +----------------------------------------------------------------+ | @@sql_mode | +----------------------------------------------------------------+ | STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +----------------------------------------------------------------+ 1 row in set (0.00 sec) mysql> exit Bye
再次进入
mysql> select @@sql_mode; +-----------------------------------------------------------------------------------+ | @@sql_mode | +-----------------------------------------------------------------------------------+ | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +-----------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
下面查看修改后的查看结果
mysql> select * from employee group by post; //只能查看post ERROR 1055 (42000): 't1.employee.id' isn't in GROUP BY mysql> select post from employee group by post; +-----------------------------------------+ | post | +-----------------------------------------+ | operation | | sale | | teacher | | 老男孩驻沙河办事处外交大使 | +-----------------------------------------+ 4 rows in set (0.00 sec) mysql> select id,post from employee group by post; ERROR 1055 (42000): 't1.employee.id' isn't in GROUP BY mysql> select name,post from employee group by post,name; //根据group by 后面的选择查看 +------------+-----------------------------------------+ | name | post | +------------+-----------------------------------------+ | 张野 | operation | | 程咬金 | operation | | 程咬铁 | operation | | 程咬铜 | operation | | 程咬银 | operation | | 丁丁 | sale | | 丫丫 | sale | | 星星 | sale | | 格格 | sale | | 歪歪 | sale | | alex | teacher | | jingliyang | teacher | | jinxin | teacher | | liwenzhou | teacher | | wupeiqi | teacher | | xiaomage | teacher | | yuanhao | teacher | | egon | 老男孩驻沙河办事处外交大使 | +------------+-----------------------------------------+ 18 rows in set (0.00 sec)
更多关于MySQL相关内容感兴趣的读者可查看本站专题：《MySQL查询技巧大全》、《MySQL常用函数大汇总》、《MySQL日志操作技巧大全》、《MySQL事务操作技巧汇总》、《MySQL存储过程技巧大全》及《MySQL数据库锁相关技巧汇总》
希望本文所述对大家MySQL数据库计有所帮助。