mysql的sql_mode 模式修改

1. sql_mode模式
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 |
+----------------------------------------------------------------+

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

或者通過查看系統變量方式:

mysql> show variables like 'sql_mode%'\G;
*************************** 1. row ***************************
Variable_name: sql_mode
Value: STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

mysql> show variables like 'sql_mode%'\G;
*************************** 1. row ***************************
Variable_name: sql_mode
        Value: 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、TRADITIONAL和STRICT_TRANS_TABLES。
ANSI模式：寬鬆模式，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。

1.2 ANSI模式

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)

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)

我們可以看到，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。

1.3 STRICT_TRANS_TABLES模式

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)

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)

我們可以看到，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。

1.3 TRADITIONAL模式

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)

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)

TRADITIONAL模式與STRICT_TRANS_TABLES模式執行的結果，在這種情況下一致。

mysql> select @@sql_mode\G;
*************************** 1. row ***************************
@@sql_mode: STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,E
RROR_FOR_DIVISION_BY_ZERO,TRADITIONAL,NO_AUTO_CREATE_USER
1 row in set (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,E
RROR_FOR_DIVISION_BY_ZERO,TRADITIONAL,NO_AUTO_CREATE_USER
1 row in set (0.00 sec)

看一下TRADITIONAL模式，我們發現在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。

注意：我們這裏設置的sql_mode都是session級別的。另外，可以直接修改my.ini文件，找到sql_mode，然後設置新的模式即可！

例如：

vi /etc/my.cnf

在[mysqld]下面添加如下列：

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES