Mysql运算符使用实战

秒速五厘米 2021-07-24 16:49 485阅读 0赞

**一 实战需求**

创建数据表，并对表中的数据进行运算操作，掌握各种运算符的使用方法。

创建表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。

使用数据表tmp15，首先创建该表，SQL语句如下：

mysql> CREATE TABLE tmp15 (note VARCHAR(100), price INT);
    Query OK, 0 rows affected (0.31 sec)

向表中插入一条记录，note值为“Thisisgood”，price值为50，SQL语句如下：

mysql> INSERT INTO tmp15 VALUES("Thisisgood", 50);
    Query OK, 1 row affected (0.04 sec)

**二 操作过程**

对表tmp15中的整型数值字段price进行算术运算，执行过程如下：

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)

对表tmp15中的整型数值字段price进行比较运算，执行过程如下：

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)

判断price值是否落在30~80区间；返回与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，执行过程如下：

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)

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’，执行过程如下：

将price字段值与NULL，0进行逻辑运算，执行过程如下：

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)

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，执行过程如下：

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)

将price字段值分别左移和右移两位，执行过程如下：

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