MYSQL入门学习之六：MYSQL的运算符_MySQL

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MYSQL入门学习之六：MYSQL的运算符

相关链接：

MYSQL入门学习之一：基本操作

http:///database/201212/173868.html

MYSQL入门学习之二：使用正则表达式搜索

http:///database/201212/173869.html

MYSQL入门学习之三：全文本搜索

http:///database/201212/173873.html

MYSQL入门学习之四：MYSQL的数据类型

http:///database/201212/175536.html

MYSQL入门学习之五：MYSQL的字符集

http:///database/201212/175541.html

一、算术运算符

1、加

mysql> select 1+2;

+-----+

| 1+2 |

+-----+

| 3 |

+-----+

2、减

mysql> select 1-2;

+-----+

| 1-2 |

+-----+

| -1 |

+-----+

3、乘

mysql> select 2*3;

+-----+

| 2*3 |

+-----+

| 6 |

+-----+

4、除

mysql> select 2/3;

+--------+

| 2/3 |

+--------+

| 0.6667 |

+--------+

5、商

mysql> select 10 p 4;

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

| 10 p 4 |

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

| 2 |

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

6、取余

mysql> select 10 MOD 4;

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

| 10 MOD 4 |

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

| 2 |

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

二、比较运算符

1、等于

mysql> select 2=3;

+-----+

| 2=3 |

+-----+

| 0 |

+-----+

mysql> select NULL = NULL;

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

| NULL = NULL |

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

| NULL |

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

2、不等于

mysql> select 23;

+------+

| 23 |

+------+

| 1 |

+------+

3、安全等于

与“=”的区别在于当两个操作码均为NULL时，其所得值为1而不为NULL，而当一个操作码为NULL时，其所得值为0而不为NULL。

mysql> select 23;

+-------+

| 23 |

+-------+

| 0 |

+-------+

mysql> select null=null;

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

| null=null |

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

| NULL |

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

mysql> select nullnull;

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

| nullnull |

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

| 1 |

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

4、小于

mysql> select 2

+-----+

| 2

+-----+

| 1 |

+-----+

5、小于等于

mysql> select 2

+------+

| 2

+------+

| 1 |

+------+

6、大于

mysql> select 2>3;

+-----+

| 2>3 |

+-----+

| 0 |

+-----+

7、大于等于

mysql> select 2>=3;

+------+

| 2>=3 |

+------+

| 0 |

+------+

8、BETWEEN

mysql> select 5 between 1 and 10;

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

| 5 between 1 and 10 |

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

| 1 |

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

9、IN

mysql> select 5 in (1,2,3,4,5);

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

| 5 in (1,2,3,4,5) |

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

| 1 |

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

10、NOT IN

mysql> select 5 not in (1,2,3,4,5);

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

| 5 not in (1,2,3,4,5) |

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

| 0 |

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

11、IS NULL

mysql> select null is NULL;

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

| null is NULL |

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

| 1 |

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

mysql> select 'a' is NULL;

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

| 'a' is NULL |

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

| 0 |

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

12、IS NOT NULL

mysql> select null IS NOT NULL;

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

| null IS NOT NULL |

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

| 0 |

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

mysql> select 'a' IS NOT NULL;

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

| 'a' IS NOT NULL |

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

| 1 |

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

13、LIKE

mysql> select '12345' like '12%';

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

| '12345' like '12%' |

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

| 1 |

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

mysql> select '12345' like '12_';

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

| '12345' like '12_' |

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

| 0 |

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

14、REGEXP

mysql> select 'beijing' REGEXP 'jing';

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

| 'beijing' REGEXP 'jing' |

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

| 1 |

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

mysql> select 'beijing' REGEXP 'xi';

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

| 'beijing' REGEXP 'xi' |

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

| 0 |

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

三、逻辑运算符

1、与

mysql> select 2 and 0;

+---------+

| 2 and 0 |

+---------+

| 0 |

+---------+

mysql> select 2 and 1;

+---------+

| 2 and 1 |

+---------+

| 1 |

+---------+

2、或

mysql> select 2 or 0;

+--------+

| 2 or 0 |

+--------+

| 1 |

+--------+

mysql> select 2 or 1;

+--------+

| 2 or 1 |

+--------+

| 1 |

+--------+

mysql> select 0 or 0;

+--------+

| 0 or 0 |

+--------+

| 0 |

+--------+

mysql> select 1 || 0;

+--------+

| 1 || 0 |

+--------+

| 1 |

+--------+

3、非

mysql> select not 1;

+-------+

| not 1 |

+-------+

| 0 |

+-------+

mysql> select !0;

+----+

| !0 |

+----+

| 1 |

+----+

4、异或

mysql> select 1 xor 1;

+---------+

| 1 xor 1 |

+---------+

| 0 |

+---------+

mysql> select 0 xor 0;

+---------+

| 0 xor 0 |

+---------+

| 0 |

+---------+

mysql> select 1 xor 0;

+---------+

| 1 xor 0 |

+---------+

| 1 |

+---------+

mysql> select null or 1;

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

| null or 1 |

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

| 1 |

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

mysql> select 1 ^ 0;

+-------+

| 1 ^ 0 |

+-------+

| 1 |

+-------+

四、位运算符

1、按位与

mysql> select 3&5;

+-----+

| 3&5 |

+-----+

| 1 |

+-----+

2、按位或

mysql> select 3|5;

+-----+

| 3|5 |

+-----+

| 7 |

+-----+

3、按位异或

mysql> select 3^5;

+-----+

| 3^5 |

+-----+

| 6 |

+-----+

4、按位取反

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

| ~3 |

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

| 18446744073709551612 |

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

mysql> select ~18446744073709551612;

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

| ~18446744073709551612 |

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

| 3 |

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

5、按位右移

mysql> select 3>>1;

+------+

| 3>>1 |

+------+

| 1 |

+------+

6、按位左移

mysql> select 3

+------+

| 3

+------+

| 6 |

+------+

五、运算符优先级顺序

最高优先级 :=

1 ||, OR, XOR

2 &&, AND

3 BETWEEN, CASE, WHEN, THEN, ELSE

4 =, , >=, >, , !=, IS, LIKE, REGEXP, IN

5 |

6 &

7 >

8 -, +

9 *, /, p, %, MOD

10 ^

11 - (unary minus), ~ (unary bit inversion)

12 !, NOT

最低优先级 BINARY, COLLATE

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