MySQL 查询合并
如果我们需要将两个select语句的结果作为一个整体显示出来，我们就需要用到union或者union all关键字。union(或称为联合)的作用是将多个结果合并在一起显示出来。
注意：两个列表中的字段要一样才可以合并(顺序也要一样)
满足条件：
1、两个select查询的列的数量必须相同；
2、每个列的数据类型需要相似；
1.先写两条select
第一条select：
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SELECT DATE_FORMAT(add_time, '%Y-%m-%d') as 'add_time', COUNT(add_time) as 'reach_intention'FROM table1where## where 条件可以根据自己实际情况来定 DATE_FORMAT(add_time, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 1 month), '%Y-%m-%d')group by DATE_FORMAT(add_time, '%Y-%m-%d') |
这是查询出来的结果
第二条select：
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select DATE_FORMAT(add_date, '%Y-%m-%d') as 'add_time' , COUNT(add_date) as 'post_release'from table2where## where 条件可以根据自己实际情况来定 DATE_FORMAT(add_date, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 1 month), '%Y-%m-%d')group by DATE_FORMAT(add_date, '%Y-%m-%d') |
第二条select查询出来的结果
2.合并查询结果
先把两条select用union all连接起来
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SELECT DATE_FORMAT(add_time, '%Y-%m-%d') as 'add_time', COUNT(add_time) as 'reach_intention' , '' as 'post_release' FROM table1 where DATE_FORMAT(add_time, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 30 day), '%Y-%m-%d') group by DATE_FORMAT(add_time, '%Y-%m-%d')UNION ALL select DATE_FORMAT(add_date, '%Y-%m-%d') as 'add_time' , '' as 'reach_intention' , COUNT(add_date) as 'post_release' from table2 where DATE_FORMAT(add_date, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 30 day), '%Y-%m-%d') group by DATE_FORMAT(add_date, '%Y-%m-%d') |
在外层嵌套一个select
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## 括号里面放 用 union all 连接的selectselect * from () test## 这里要给表起个别名 不然会报 Every derived table must have its own alias 每个派生表都必须有自己的别名 |
把union all 连接的select 放到括号里面去然后运行
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select *from( SELECT DATE_FORMAT(add_time, '%Y-%m-%d') as 'add_time', COUNT(add_time) as 'reach_intention' , '' as 'post_release' FROM table1 where DATE_FORMAT(add_time, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 30 day), '%Y-%m-%d') group by DATE_FORMAT(add_time, '%Y-%m-%d')UNION ALL select DATE_FORMAT(add_date, '%Y-%m-%d') as 'add_time' , '' as 'reach_intention' , COUNT(add_date) as 'post_release' from table2 where DATE_FORMAT(add_date, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 30 day), '%Y-%m-%d') group by DATE_FORMAT(add_date, '%Y-%m-%d') ) test |
运行结果
把结果按日期分组排序。
使用 group by 和 order by 关键字
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select add_time, sum(reach_intention) as 'reach_intention' , sum(post_release) as 'post_release'from ( SELECT DATE_FORMAT(add_time, '%Y-%m-%d') as 'add_time', COUNT(add_time) as 'reach_intention' , '' as 'post_release' FROM table1 where DATE_FORMAT(add_time, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 30 day), '%Y-%m-%d') group by DATE_FORMAT(add_time, '%Y-%m-%d')UNION ALL select DATE_FORMAT(add_date, '%Y-%m-%d') as 'add_time' , '' as 'reach_intention' , COUNT(add_date) as 'post_release' from table2 where DATE_FORMAT(add_date, '%Y-%m-%d') > DATE_FORMAT(date_sub(now(), interval 30 day), '%Y-%m-%d') group by DATE_FORMAT(add_date, '%Y-%m-%d') ) testgroup by test.add_timeorder by test.add_time desc |
结果如下
总结
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原文链接：https://blog.csdn.net/m0_49245543/article/details/117289851
