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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