SQL_MODE设置

1.1.   SQL_MODE设置

         在生产环境中强烈建议将这个值设置为严格模式，这样有些问题可以在数据库的设计和开发阶段就能实现，而如果在生产环境下运行数据库后发现这类问题，那么修改的代价将变得十分巨大。此外正确地设置sql_mode还可以做一些约束（constraint）检查的工作。

         对于sql_mode的设置，可以在配置文件、客户端、当前会话或者全局会话中设置。查看sql_mode的设置情况：

mysql>select @@global.sql_mode;

+--------------------------------------------+

|@@global.sql_mode                         |

+--------------------------------------------+

|STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION |

+--------------------------------------------+

1 row inset (0.00 sec)

mysql>select @@session.sql_mode;

+--------------------------------------------+

|@@session.sql_mode                        |

+--------------------------------------------+

|STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION |

+--------------------------------------------+

1 row inset (0.00 sec)

1.1.1.     STRICT_TRANS_TABLES

         严格模式是指将sql_mode变量设置为STRICT_TRANS_TABLES或STRICT_ALL_TABLES中的至少一种

         STRICT_TRANS_TABLES：在该模式下，如果一个值不能插入到一个事务表，则中断当前的操作不影响非事务表（例如表的存储引擎为myisam）；

1.1.2.     ALLOWS_INVALID_DATES

         该选项并不完全对日期的合法性进行检查，只检查月份是否在1-12之间，日期是否在1-31之间。该模式仅对date和datetime类型有效，而对timestamp无效，因为timestamp总是要求一个合法的输入。

1.1.3.     ANSI_QUOTES

         启用ANSI_QUOTES后，不能使用双引号来引用字符串，因为它将被解释为识别符。

mysql>create table z(a varchar(10))engine=innodb;

Query OK,0 rows affected (0.02 sec)

mysql>insert into z select "aaa";

Query OK,1 row affected (0.01 sec)

Records:1  Duplicates: 0  Warnings: 0

mysql>set sql_mode=‘ANSI_QUOTES‘;

Query OK,0 rows affected (0.00 sec)

mysql>insert into z select "aaa";

ERROR1054 (42S22): Unknown column ‘aaa‘ in ‘field list‘

mysql>

1.1.4.     ERROR_FOR_DIVISION_BY_ZERO

         在insert或者update过程中，如果数据被零除（或MOD(X,0))则产生错误（否则为警告）。如果未给出该模式，那么数据被零除时，mysql返回NULL。如果用到INSERT IGNORE或者UPDATE IGNORE中，mysql生成被零除警告，但操作结果为NULL。

1.1.5.     HIGH_NOT_PRECEDENCE

         启用HIGH_NOT_PRECEDENCE：操作符的优先顺序表达式。例如not a between b and c被解释为NOT (a between a and b)。启用HIGH_NOT_PRECEDENCE SQL模式，可以获得以前版本的更高优先级的结果。

mysql>select 0 between -1 and 1;

+--------------------+

| 0between -1 and 1 |

+--------------------+

|                  1 |

+--------------------+

1 row inset (0.00 sec)

mysql>select not 0 between -1 and 1;

+------------------------+

| not 0between -1 and 1 |

+------------------------+

|                      0 |

+------------------------+

1 row inset (0.00 sec)

mysql>set sql_mode=‘high_not_precedence‘;

Query OK,0 rows affected (0.00 sec)

mysql>select 0 between -1 and 1;

+--------------------+

| 0between -1 and 1 |

+--------------------+

|                  1 |

+--------------------+

1 row inset (0.01 sec)

mysql>select not 0 between -1 and 1;

+------------------------+

| not 0between -1 and 1 |

+------------------------+

|                      1 |

+------------------------+

1 row inset (0.00 sec)

         被解释为（not 0） between -1 and 1结果完全相反。

1.1.6.     ignore_space

         忽略函数名和括号之间的空格：

mysql>select max(a) from t;

+--------+

| max(a)|

+--------+

|    105 |

+--------+

1 row inset (0.00 sec)

mysql>select max (a) fromt;

ERROR1630 (42000): FUNCTION test.max does not exist. Check the ‘Function NameParsing and Resolution‘ section in the Reference Manual

mysql>set sql_mode=‘ignore_space‘;

Query OK,0 rows affected (0.00 sec)

mysql>select max (a) from t;

+---------+

| max (a)|

+---------+

|     105 |

+---------+

1 row inset (0.00 sec)

1.1.7.     NO_AUTO_CREATE_USER

         禁止grant创建密码为空的用户

mysql>select @@sql_mode;

+---------------------+

|@@sql_mode          |

+---------------------+

|NO_AUTO_CREATE_USER |

+---------------------+

1 row inset (0.00 sec)

mysql>set sql_mode=‘‘;

Query OK,0 rows affected (0.00 sec)

mysql>grant all privileges on *.* to gf@‘%‘;

Query OK,0 rows affected (0.00 sec)

mysql>set sql_mode=‘NO_AUTO_CREATE_USER‘;

Query OK,0 rows affected (0.00 sec)

mysql>grant all privileges on *.* to gf1@‘%‘;

ERROR1133 (42000): Can‘t find any matching row in the user table

mysql>grant all privileges on *.* to gf1@‘%‘ identified by 123456;

ERROR1064 (42000): You have an error in your SQL syntax; check the manual thatcorresponds to your MySQL server version for the right syntax to use near‘123456‘ at line 1

mysql>grant all privileges on *.* to gf5@‘%‘ identified by 123456;

ERROR1064 (42000): You have an error in your SQL syntax; check the manual thatcorresponds to your MySQL server version for the right syntax to use near‘123456‘ at line 1

1.1.8.     NO_AUTO_VALUE_ON_ZERO

         该选项影响列为自增长的插入。在默认设置下，插入0或者null代表生成下一个自增长值。如果用户希望插入的值为0，而该列又是自增长的，那么这个选项就有用了。

mysql>create table tt(id int primary key auto_increment);

Query OK,0 rows affected (0.02 sec)

mysql>explain tt\G;

***************************1. row ***************************

  Field: id

   Type: int(11)

   Null: NO

    Key: PRI

Default:NULL

  Extra: auto_increment

1 row inset (0.00 sec)

ERROR:

No queryspecified

mysql>insert into tt values(0);

Query OK,1 row affected (0.02 sec)

mysql>insert into tt values(null);

Query OK,1 row affected (0.00 sec)

mysql>insert into tt values(5);

Query OK,1 row affected (0.00 sec)

mysql>select * from tt;

+----+

| id |

+----+

|  2 |

|  4 |

|  5 |

+----+

3 rows inset (0.00 sec)

mysql>set sql_mode=‘no_auto_value_on_zero‘;

Query OK,0 rows affected (0.00 sec)

mysql>truncate table tt;

Query OK,0 rows affected (0.01 sec)

mysql>insert into tt values(0);

Query OK,1 row affected (0.01 sec)

mysql>insert into tt values(null);

Query OK,1 row affected (0.00 sec)

mysql>insert into tt values(5);

Query OK,1 row affected (0.01 sec)

mysql>select * from tt;

+----+

| id |

+----+

|  0 |

|  2 |

|  5 |

+----+

3 rows inset (0.01 sec)

         只是对0插入有效。

1.1.9.     NO_BACKSLASH_ESCAPES

         反斜杠“\”作为普通字符而非转义字符：

mysql>set sql_mode=‘NO_BACKSLASH_ESCAPES‘;

Query OK,0 rows affected (0.00 sec)

mysql>select ‘\\‘\G;

***************************1. row ***************************

\\: \\

1 row inset (0.00 sec)

ERROR:

No queryspecified

mysql>set sql_mode=‘‘;

Query OK,0 rows affected (0.00 sec)

mysql>select ‘\\‘\G;

***************************1. row ***************************

\: \

1 row inset (0.00 sec)

1.1.10. NO_DIR_IN_CREATE

         在创建表时忽视所有INDEXDIRETORY和DATA DIRECTORY的选项。

1.1.11. NO_ENGINE_SUBSTITUTION

         如果需要的存储引擎被禁用或者未编译，那么抛出错误。

1.1.12. NO_UNSIGNED_SUBSTITUTION

         启用这个选项后，两个UNSIGNED类型相减返回SIGNED类型。

1.1.13. NO_ZERO_DATE

         在非严格模式下，可以插入形如“00-00-0000:00:00”的非法日期，mysql仅抛出一个警告，而启用该选项后，mysql不允许插入零日期，插入0日期会抛出错误而非警告。

mysql>set sql_mode=‘no_zero_date,strict_trans_tables‘;

Query OK,0 rows affected, 1 warning (0.00 sec)

mysql>insert into tt values(null,‘00-00-00 00:00:00‘);

ERROR1292 (22007): Incorrect datetime value: ‘00-00-00 00:00:00‘ for column ‘date‘at row 1

mysql>insert into tt values(null,‘2014-12-02 00:00:00‘);

Query OK,1 row affected (0.01 sec)

mysql>select * from tt;

+----+---------------------+

| id |date                |

+----+---------------------+

|  0 | NULL                |

|  2 | NULL                |

|  5 | NULL                |

|  6 | NULL                |

|  8 | 0000-00-00 00:00:00 |

| 10 |0000-00-00 00:00:00 |

| 12 |0000-00-00 00:00:00 |

| 14 |2014-12-02 00:00:00 |

+----+---------------------+

8 rows inset (0.00 sec)

         注意一定是在strict_trans_tables，否则只是警告：

mysql>set sql_mode=‘no_zero_date‘;

Query OK,0 rows affected, 1 warning (0.00 sec)

mysql>insert into tt values(null,‘00-00-00 00:00:00‘);

Query OK,1 row affected, 1 warning (0.00 sec)

mysql>show warnings;

+---------+------+-----------------------------------------------+

| Level   | Code | Message                                       |

+---------+------+-----------------------------------------------+

| Warning| 1264 | Out of range value for column ‘date‘ at row 1 |

+---------+------+-----------------------------------------------+

1 row inset (0.00 sec)

mysql>select * from tt;

+----+---------------------+

| id |date                |

+----+---------------------+

|  0 | NULL                |

|  2 | NULL                |

|  5 | NULL                |

|  6 | NULL                |

|  8 | 0000-00-00 00:00:00 |

| 10 |0000-00-00 00:00:00 |

+----+---------------------+

6 rows inset (0.00 sec)

1.1.14. NO_ZERO_IN_DATE

         在严格模式下，不允许日期和月份为零：采用日期和月份为零的格式时mysql会直接抛出错误而非警告：

mysql>set sql_mode=‘NO_ZERO_IN_DATE‘;

Query OK,0 rows affected, 1 warning (0.00 sec)

mysql>TRUNCATE TABLE tt;

Query OK,0 rows affected (0.00 sec)

mysql>insert into tt values(null,‘2014-12-02 00:00:00‘);

Query OK,1 row affected (0.00 sec)

mysql>insert into tt values(null,‘2014-12-00 00:00:00‘);

Query OK,1 row affected, 1 warning (0.00 sec)

mysql>show warnings;

+---------+------+-----------------------------------------------+

|Level   | Code | Message                                       |

+---------+------+-----------------------------------------------+

| Warning| 1264 | Out of range value for column ‘date‘ at row 1 |

+---------+------+-----------------------------------------------+

1 row in set(0.00 sec)

mysql>select * from tt;

+----+---------------------+

| id |date                |

+----+---------------------+

|  1 | 2014-12-02 00:00:00 |

|  2 | 0000-00-00 00:00:00 |

+----+---------------------+

2 rows inset (0.00 sec)

mysql>set sql_mode=‘NO_ZERO_IN_DATE,strict_trans_tables‘;

Query OK,0 rows affected, 1 warning (0.00 sec)

mysql>insert into tt values(null,‘2014-12-00 00:00:00‘);

ERROR1292 (22007): Incorrect datetime value: ‘2014-12-00 00:00:00‘ for column ‘date‘at row 1

mysql>

1.1.15. ONLY_FULL_GROUP_BY

         对于GROUP by聚合操作，如果在select中的列没有在GROUP BY中出现，那么sql语句是不合法的，因为a列不在group by从句中。

mysql>select id,sum(date) from tt group by date;

+----+----------------+

| id |sum(date)      |

+----+----------------+

|  2 |              0 |

|  1 | 20141202000000 |

+----+----------------+

2 rows inset (0.00 sec)

mysql>set sql_mode=‘ONLY_FULL_GROUP_BY‘;

Query OK,0 rows affected (0.00 sec)

mysql>select id,sum(date) from tt group by date;

ERROR1055 (42000): ‘gf.tt.id‘ isn‘t in GROUP BY

mysql>

1.1.16. PAD_CHAR_TO_FULL_LENGTH

         对于char类型，不要截断空洞数据。空洞数据就是自动填充值为0x20的数据。

         默认情况下：

mysql>create table ttt(a char(5));

Query OK,0 rows affected (0.01 sec)

mysql>insert into ttt select ‘a‘;

Query OK,1 row affected (0.00 sec)

Records:1  Duplicates: 0  Warnings: 0

mysql>select a,char_length(a),hex(a) from ttt;

+------+----------------+--------+

| a    | char_length(a) | hex(a) |

+------+----------------+--------+

| a    |              1 | 61     |

+------+----------------+--------+

1 row inset (0.00 sec)

         默认字符长度为1，数据库对后面的空洞数据进行了截断。

mysql>set sql_mode=‘pad_char_to_full_length‘;

Query OK,0 rows affected (0.00 sec)

mysql>select a,char_length(a),hex(a) from ttt;

+-------+----------------+------------+

| a     | char_length(a) | hex(a)     |

+-------+----------------+------------+

| a     |              5 | 6120202020 |

+-------+----------------+------------+

1 row inset (0.00 sec)

         反映的是实际存储的内容。

1.1.17. PIPES_AS_CONCAT

         将“||”视为字符串的联接操作符而非运算符，这个和oracle数据库是一样的，也和字符串的拼接函数concat相类似。

mysql>select ‘a‘||‘b‘||‘c‘;

+---------------+

|‘a‘||‘b‘||‘c‘ |

+---------------+

|             0 |

+---------------+

1 row inset, 3 warnings (0.00 sec)

mysql>show warnings;

+---------+------+---------------------------------------+

|Level   | Code | Message                               |

+---------+------+---------------------------------------+

| Warning| 1292 | Truncated incorrect DOUBLE value: ‘a‘ |

| Warning| 1292 | Truncated incorrect DOUBLE value: ‘b‘ |

| Warning| 1292 | Truncated incorrect DOUBLE value: ‘c‘ |

+---------+------+---------------------------------------+

3 rows inset (0.00 sec)

mysql>set sql_mode=‘pipes_as_concat‘;

Query OK,0 rows affected (0.00 sec)

mysql>select ‘a‘||‘b‘||‘c‘;

+---------------+

|‘a‘||‘b‘||‘c‘ |

+---------------+

|abc           |

+---------------+

1 row inset (0.00 sec)

1.1.18. REAL_AS_FLOAT

         将real视为float的同义词而不是double的同义词。

1.1.19. STRICT_ALL_TABLES

         对所有引擎的表都启用严格模式。STRICT_TRANS_TABLES只对支持事务的表启用严格模式。

         在严格模式下，一旦任何操作的数据产生问题，都会终止当前的操作。

         对于启用STRICT_ALL_TABLES选项的非事务引擎来说，这时数据可能停留在一个未知的状态，这可能不是所有非事务引擎原意看到的一种情况，因此需要非常小心这个选项可能带来的潜在影响。

1.1.20. SQL_MODE的选项组合