mysql中的sql_mode

mysql數據庫的中有一個環境變量sql_mode,定義了mysql應該支持的sql語法，數據校驗等！我們可以通過以下方式查看當前數據庫使用的sql_mode：

mysql> select @@sql_mode;  
+----------------------------------------------------------------+  
| @@sql_mode                                                     |  
+----------------------------------------------------------------+  
| STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |  
+----------------------------------------------------------------+ 

mysql5.0以上版本支持三種sql_mode模式

ANSI模式	寬松模式，對插入數據進行校驗，如果不符合定義類型或長度，對數據類型調整或截斷保存，報warning警告。
TRADITIONAL模式	嚴格模式，當向mysql數據庫插入數據時，進行數據的嚴格校驗，保證錯誤數據不能插入，報error錯誤。用於事物時，會進行事物的回滾。
STRICT_TRANS_TABLES模式	嚴格模式，進行數據的嚴格校驗，錯誤數據不能插入，報error錯誤。

1 ANSI模式 

在ANSI模式下，當我們插入數據時，未滿足列長度要求時，數據同樣會插入成功，但是對超出列長度的字段進行截斷，同時報告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，當我們插入數據時，mysql會嚴格的進行數據的校驗，當發現插入列值未滿足要求，直接報告error錯誤，保證了錯誤數據無法插入到數據庫中。

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，初看結果是不是一樣

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，可以看看設置后的情況

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，對所有的事務存儲引擎，非事務存儲引擎檢查，日期類型中的月和日部分不能包含0，不能有0這樣的日期(0000-00-00),數據不能除0，禁止grant自動創建新用戶等一些校驗。

最后：

set @@只是在sessions級別設置的，要想所有的都生效，還是要設置配置文件

vi /etc/my.cnf

在[mysqld]下面添加如下列：

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

#NO_ENGINE_SUBSTITUTION對於不存在的引擎就報錯，不加的話，指定不支持的引擎時指定默認的innodb

另外：sql_mode還有一個配置ONLY_FULL_GROUP_BY，這個表示采用group by帥選數據的時候只能查看新組內信息

 

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 | 張野   | 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 | 老男孩駐沙河辦事處外交大使              | NULL         |    7300.33 |    401 |         1 |
+----+--------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
4 rows in set (0.00 sec)

此時的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，退出再進入才會生效

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
再次進入

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結果

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                                 |
| 老男孩駐沙河辦事處外交大使              |
+-----------------------------------------+
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;  //根據group by 后面的選擇查看
+------------+-----------------------------------------+
| name | post |
+------------+-----------------------------------------+
| 張野 | operation |
| 程咬金 | operation |
| 程咬鐵 | operation |
| 程咬銅 | operation |
| 程咬銀 | 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 | 老男孩駐沙河辦事處外交大使 |
+------------+-----------------------------------------+
18 rows in set (0.00 sec)