MySQL 5.7 SQL MODE严格模式带来的影响

时间 2019-11-08

标签 mysql 5.7 sql mode 严格模式带来影响栏目 MySQL 繁體版

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背景：在以前的升级过程当中，为了对RD更加友好的支持，咱们都是把MySQL的SQL MODE修改为低版本的，可是这样每每也会带来一些其余问题，今天咱们就来梳理一下，SQL MODE在MySQL 5.6和5.7两个版本之间的差别，让DBA在后续的升级过程当中，更加从容。html

1、如何查看如今MySQL的SQL MODE

1.1 查看mysql的sql mode：

# MySQL 5.6 Default SQL_MODE;

mysql> select @@sql_mode;

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

| @@sql_mode                                 |

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

| NO_ENGINE_SUBSTITUTION |

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

1 row in set (0.00 sec)



# MySQL 5.7 Default SQL_MODE;

mysql> select @@sql_mode;

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

| @@sql_mode                                                                                                                                |

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

| ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |

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

1 row in set (0.00 sec)

1.2 简单解释下5.7的默认SQL MODE

ONLY_FULL_GROUP_BY

在select、having、group by列表里引用的列必须在group by列表中，不然报错。mysql

STRICT_TRANS_TABLES

严格模式控制MySQL如何处理非法或丢失的输入值的SQL。有几种缘由可使一个值为非法。例如，数据类型错误或超出范围。当新插入的行不包含某列的没有显示定义DEFAULT子句的值，则该值被丢失。sql

对于事务表，当启用STRICT_ALL_TABLES或STRICT_TRANS_TABLES模式时，若是语句中有非法或丢失值，则会出现错误。SQL语句被回滚。ui

对于非事务表，STRICT_TRANS_TABLES，MySQL将非法值转换为最接近该列的合法值并插入调整后的值。若是值丢失，MySQL在列中插入隐式默认值。在任何状况下，MySQL都会生成警告而不是给出错误并继续执行语句。this

若是你不使用严格模式(即不启用STRICT_TRANS_TABLES或STRICT_ALL_TABLES模式)，对于非法或丢失的值，MySQL将插入调整后的值并给出警告。在严格模式，你能够经过INSERT IGNORE或UPDATE IGNORE来实现。spa

NO_ZERO_IN_DATE

在严格模式，不接受月或日部分为0的日期，对年不限制。若是使用IGNORE选项，咱们为相似的日期插入’0000-00-00’。在非严格模式，能够接受该日期，但会生成警告。code

NO_ZERO_DATE

在严格模式，不要将’0000-00-00’作为合法日期。你仍然能够用IGNORE选项插入零日期。在非严格模式，能够接受该日期，但会生成警告。orm

ERROR_FOR_DIVISION_BY_ZERO

在严格模式，在INSERT或UPDATE过程当中，若是被零除(或MOD(X，0))，则产生错误(不然为警告)。若是未给出该模式，被零除时MySQL返回NULL。若是用到INSERT IGNORE或UPDATE IGNORE中，MySQL生成被零除警告，但操做结果为NULL。htm

NO_AUTO_CREATE_USER

在严格模式下，防止GRANT自动建立新用户，除非还指定了密码。blog

2、验证SQL MODE对SQL的影响

2.1 group by语句的影响

mysql> select @@sql_mode;
+-------------------------------------------+
| @@sql_mode                                |
+-------------------------------------------+
| ONLY_FULL_GROUP_BY,NO_ENGINE_SUBSTITUTION |
+-------------------------------------------+
1 row in set (0.00 sec)

mysql> select * from words group by id;
ERROR 1055 (42000): 'tom.words.word' isn't in GROUP BY

mysql> select id,count(word) from words group by word;
ERROR 1055 (42000): 'tom.words.id' isn't in GROUP BY

mysql> select id,word,count(word) from words group by word;
ERROR 1055 (42000): 'tom.words.id' isn't in GROUP BY

mysql> select word,count(word) from words group by word having count(word)>1;
+------+-------------+
| word | count(word) |
+------+-------------+
| bbbb |           3 |
+------+-------------+
1 row in set (0.00 sec)

mysql> select * from words;
+----+------+
| id | word |
+----+------+
|  1 | aaaa |
|  2 | bbbb |
|  3 | cccc |
|  4 | bbbb |
|  5 | bbbb |
+----+------+
5 rows in set (0.00 sec)

2.2 日期零值的影响

mysql> CREATE TABLE `test` (`time` datetime NOT NULL DEFAULT '1111-00-01 00:00:00'  ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@sql_mode;
+-------------------------------------------+
| @@sql_mode                                |
+-------------------------------------------+
| ONLY_FULL_GROUP_BY,NO_ENGINE_SUBSTITUTION |
+-------------------------------------------+
1 row in set (0.00 sec)

mysql> set sql_mode='ONLY_FULL_GROUP_BY,NO_ENGINE_SUBSTITUTION,NO_ZERO_IN_DATE,NO_ZERO_DATE';
Query OK, 0 rows affected, 2 warnings (0.00 sec)

mysql> drop table test;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE `test` (`time` datetime NOT NULL DEFAULT '1111-00-01 00:00:00'  ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
Query OK, 0 rows affected, 1 warning (0.01 sec)

mysql> select @@sql_mode;
+------------------------------------------------------------------------+
| @@sql_mode                                                             |
+------------------------------------------------------------------------+
| ONLY_FULL_GROUP_BY,NO_ZERO_IN_DATE,NO_ZERO_DATE,NO_ENGINE_SUBSTITUTION |
+------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> select @@version;
+------------+
| @@version  |
+------------+
| 5.6.35-log |
+------------+
1 row in set (0.00 sec)

mysql> set sql_mode='ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
Query OK, 0 rows affected, 3 warnings (0.00 sec)

mysql> drop table test;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE `test` (`time` datetime NOT NULL DEFAULT '1111-00-01 00:00:00'  ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
ERROR 1067 (42000): Invalid default value for 'time'

下面的例子：

# 不合法默认值;

CREATE TABLE `test` (`time` datetime NOT NULL DEFAULT '1111-00-01 00:00:00'

) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;



# 合法默认值;

CREATE TABLE `test` (`time` datetime NOT NULL DEFAULT '1111-01-01 00:00:00'

) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;



# 合法默认值;

CREATE TABLE `test` (`time` datetime NOT NULL DEFAULT '0000-01-01 00:00:00'

) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

2.3 字段非法值的影响

mysql> select @@sql_mode;
+------------------------+
| @@sql_mode             |
+------------------------+
| NO_ENGINE_SUBSTITUTION |
+------------------------+
1 row in set (0.00 sec)

mysql> set sql_mode='ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
Query OK, 0 rows affected, 3 warnings (0.00 sec)

mysql> use tom
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show create table words;
+-------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                                |
+-------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| words | CREATE TABLE `words` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `word` varchar(4) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 |
+-------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> insert into words(word) values("abcde");
ERROR 1406 (22001): Data too long for column 'word' at row 1
mysql> insert into words(word) values(10/0);
ERROR 1365 (22012): Division by 0
mysql> insert into words(word) values(13);
Query OK, 1 row affected (0.00 sec)

mysql> insert into words(id) values(abc);
ERROR 1054 (42S22): Unknown column 'abc' in 'field list'

mysql> insert into words(id) values('abc');
ERROR 1366 (HY000): Incorrect integer value: 'abc' for column 'id' at row 1

mysql> alter table words change `word` `word` varchar(3) DEFAULT NULL;
ERROR 1265 (01000): Data truncated for column 'word' at row 1

mysql> alter table words change `id` `id` int(10) unsigned NOT NULL AUTO_INCREMENT;
Query OK, 7 rows affected (0.01 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> insert into words(id) values(-1);
ERROR 1264 (22003): Out of range value for column 'id' at row 1

mysql>show create table words1;
+--------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table  | Create Table                                                                                                                                            |
+--------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
| words1 | CREATE TABLE `words1` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `word` varchar(5) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+--------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> insert into words1(id) values(1);
ERROR 1364 (HY000): Field 'word' doesn't have a default value

2.4 非严格模式致使的sql执行结果不一致

##表数据以下
mysql> select * from words;
+----+------+
| id | word |
+----+------+
|  7 | aaaa |
|  8 | bbbb |
|  9 | cccc |
| 10 | bbbb |
| 11 | cccc |
+----+------+
5 rows in set (0.00 sec)

##5.6环境执行
mysql> select * from (select * from words order by id desc) a group by word  ;
+----+------+
| id | word |
+----+------+
|  7 | aaaa |
| 10 | bbbb |
| 11 | cccc |
+----+------+
3 rows in set (0.00 sec)

##5.7环境执行
mysql> select * from (select * from words order by id desc) a group by word  ;
+----+------+
| id | word |
+----+------+
|  7 | aaaa |
|  8 | bbbb |
|  9 | cccc |
+----+------+
3 rows in set (0.00 sec)

##正确的姿式
mysql> select max(id),word from (select * from words order by id desc) a group by word  ;
+---------+------+
| max(id) | word |
+---------+------+
|       7 | aaaa |
|      10 | bbbb |
|      11 | cccc |
+---------+------+
3 rows in set (0.00 sec)

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