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  • MySQL基础之 AND和OR运算符

    AND和OR运算符

      作用:用于基于一个以上的条件对记录进行过滤

      用法:可在WHERE子句中把两个或多个条件结合在一起。

      AND:如果第一个条件和第二个条件都成立,才会显示一条记录

      OR:如果第一个条件和第二个条件中只要有一个成立,则OR运算符就会显示一条记录

        如果两个条件都成立,则显示两条记录

    先来查看一下表

    mysql> select *from information;
    +------+----------+-----------------+-----------+
    | id   | name     | address         | city      |
    +------+----------+-----------------+-----------+
    | 1001 | xiaoming | NiuJin          | England   |
    | 1002 | xiaochen | Oxford street   | New York  |
    | 1003 | xiaoming | chaoyang street | Beijing   |
    | 1004 | xiaohua  | haha street     | Zhengzhou |
    +------+----------+-----------------+-----------+
    4 rows in set (0.00 sec)

    AND运算符实例

    显示名字为“xiaoing”,地址为“NiuJin”的人

    mysql> SELECT * from information WHERE name='xiaoming' AND address='NiuJin';
    +------+----------+---------+---------+
    | id   | name     | address | city    |
    +------+----------+---------+---------+
    | 1001 | xiaoming | NiuJin  | England |
    +------+----------+---------+---------+
    1 row in set (0.00 sec)

    OR运算符实例

    显示名字是“xiaoming”,或者城市是“Zhengzhou”的人

    mysql> SELECT * FROM  information WHERE name='xiaoming' OR city='Zhengzhou';
    +------+----------+-----------------+-----------+
    | id   | name     | address         | city      |
    +------+----------+-----------------+-----------+
    | 1001 | xiaoming | NiuJin          | England   |
    | 1003 | xiaoming | chaoyang street | Beijing   |
    | 1004 | xiaohua  | haha street     | Zhengzhou |
    +------+----------+-----------------+-----------+
    3 rows in set (0.00 sec)

    显示要么名字为“xiaoming”,要么城市是“England”的人

    mysql> SELECT * FROM information WHERE name='xiaochen' OR city='England';
    +------+----------+---------------+----------+
    | id   | name     | address       | city     |
    +------+----------+---------------+----------+
    | 1001 | xiaoming | NiuJin        | England  |
    | 1002 | xiaochen | Oxford street | New York |
    +------+----------+---------------+----------+
    2 rows in set (0.00 sec)

    AND 和 OR 的复杂结合(使用圆括号来组成复杂的表达式)

    这种表达式比较的复杂,但也是常见的。

    mysql> SELECT name,address,city  FROM information WHERE (city='England' OR city='Beijing') AND name='xiaoming';
    +----------+-----------------+---------+
    | name     | address         | city    |
    +----------+-----------------+---------+
    | xiaoming | NiuJin          | England |
    | xiaoming | chaoyang street | Beijing |
    +----------+-----------------+---------+
    2 rows in set (0.00 sec)

    这种适用于我们已经定好一个查询条件的内容,另外一个条件的内容待定的情况

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  • 原文地址:https://www.cnblogs.com/FengGeBlog/p/9783775.html
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