mysql中运算符的使用示例

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案例：创建数据表tmp15，其中包含varchar类型的字段note和int类型的字段price。

• 使用运算符对表tmp15中不同的字段进行运算。

• 使用逻辑操作符对数据进行逻辑操作。

• 使用位操作符对数据进行位操作。

首先创建tmp15表，插入一条记录，note值为"Thisisgood"，price值为50，SQL语句如下：

mysql> create table tmp15    -> (    -> note varchar(100),    -> price int    -> );Query OK, 0 rows affected (0.13 sec)mysql> into tmp15 values    -> (    -> "Thisisgood",50    -> );    mysql> insert into tmp15 values    -> ("Thisisgood",50);Query OK, 1 row affected (0.06 sec)

(1)对表tmp15中的整型数值字段price进行算数运算，SQL语句如下：

mysql> select price,    -> price + 10,    -> price - 10,    -> price * 2,    -> price / 2,    -> price % 3    -> from tmp15;+-------+------------+------------+-----------+-----------+-----------+| price | price + 10 | price - 10 | price * 2 | price / 2 | price % 3 |+-------+------------+------------+-----------+-----------+-----------+|    50 |         60 |         40 |       100 |   25.0000 |         2 |+-------+------------+------------+-----------+-----------+-----------+1 row in set (0.00 sec)

(2)对表tmp15中的整型数值字段price进行比较运算，SQL语句如下：

mysql> select price,    -> price>10,    -> price<10,    -> price != 10,    -> price = 10,    -> price<=>10,    -> price<>10    -> from tmp15;+-------+----------+----------+-------------+------------+------------+-----------+| price | price>10 | price<10 | price != 10 | price = 10 | price<=>10 | price<>10 |+-------+----------+----------+-------------+------------+------------+-----------+|    50 |        1 |        0 |           1 |          0 |          0 |         1 |+-------+----------+----------+-------------+------------+------------+-----------+1 row in set (0.00 sec)

(3)判断price值是否落在30-80区间、返回70、30相比最大的值、判断price是否为in列表(10、20、50、35)中的某个值，SQL语句如下：

mysql> select price,    -> price between 30 and 80,    -> greatest(price,70,30),    -> price in(10,20,50,35)    -> from tmp15;+-------+-------------------------+-----------------------+-----------------------+| price | price between 30 and 80 | greatest(price,70,30) | price in(10,20,50,35) |+-------+-------------------------+-----------------------+-----------------------+|    50 |                       1 |                    70 |                     1 |+-------+-------------------------+-----------------------+-----------------------+1 row in set (0.00 sec)

(4)对tmp15中的字符串数值字段note进行比较运算，判断表tmp15中note字段是否为空、使用LIKE判断是否以字母"t"开头、使用regexp判断是否以字母"y"结尾、判断是否包含字母"g"或者"m"，SQL语句如下：

mysql> select note,    -> note is null,    -> note like 't%',    -> note regexp '$y',    -> note regexp '[gm]'    -> from tmp15;+------------+--------------+----------------+------------------+--------------------+| note       | note is null | note like 't%' | note regexp '$y' | note regexp '[gm]' |+------------+--------------+----------------+------------------+--------------------+| Thisisgood |            0 |              1 |                0 |                  1 |+------------+--------------+----------------+------------------+--------------------+1 row in set (0.05 sec)

(5)将price字段值与null、0进行逻辑运算，SQL语句如下：

mysql> select price,    -> price && 1,    -> price && null,    -> price || 0,    -> price and 0,    -> 0 and null,    -> price or null    -> from tmp15;+-------+------------+---------------+------------+-------------+------------+---------------+| price | price && 1 | price && null | price || 0 | price and 0 | 0 and null | price or null |+-------+------------+---------------+------------+-------------+------------+---------------+|    50 |          1 |          NULL |          1 |           0 |          0 |             1 |+-------+------------+---------------+------------+-------------+------------+---------------+1 row in set (0.00 sec)mysql> select price,    -> !price,    -> not null,    -> price xor 3,    -> 0 xor null,    -> price xor 0    -> from tmp15;+-------+--------+----------+-------------+------------+-------------+| price | !price | not null | price xor 3 | 0 xor null | price xor 0 |+-------+--------+----------+-------------+------------+-------------+|    50 |      0 |     NULL |           0 |       NULL |           1 |+-------+--------+----------+-------------+------------+-------------+1 row in set (0.00 sec)

(6)将price字段值与2、4进行按位与、按位或 操作，并对price进行按位操作，SQL语句如下：

mysql> select price,    -> price & 2,    -> price | 4,    -> ~price from tmp15;+-------+-----------+-----------+----------------------+| price | price & 2 | price | 4 | ~price               |+-------+-----------+-----------+----------------------+|    50 |         2 |        54 | 18446744073709551565 |+-------+-----------+-----------+----------------------+1 row in set (0.00 sec)

(7)将price字段值分别额左移和右移两位，SQL语句如下：

mysql> select  price,    -> price<<2,    -> price>>2    -> from tmp15;+-------+----------+----------+| price | price<<2 | price>>2 |+-------+----------+----------+|    50 |      200 |       12 |+-------+----------+----------+1 row in set (0.00 sec)

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