MySQL 对两个表中的列进行合并计数答案

【问题标题】：MySQL combine counts on columns from two tablesMySQL 对两个表中的列进行合并计数
【发布时间】：2020-10-07 16:58:14
【问题描述】：

有没有办法将这两个查询组合成一个 where table1.column1 = table2.column1 以便它返回以下内容？

select column1, count(column1) as var1 from table1 where  datediff(now(),createdAt) = 0 group by column1

select column1, count(column1) as var2 from table2 where  datediff(now(),createdAt) = 0 group by column1

column1, var1, var2
column1, var1, var2
column1, var1, var2
column1, var1, var2

【问题讨论】：

你试过子查询和join吗？
我尝试过但无法获得正确的语法，并且与 union 相同
select t1.column1, t1.var1, t2.var2 (select column1, count(column1) as var1 from table1 where datediff(now(),createdAt) = 0 group by column1) t1, ( select column1, count(column1) as var2 from table2 where datediff(now(),createdAt) = 0 group by column1) t2 where t1.column1= t2.column1

标签： mysql sql

【解决方案1】：

使用子查询和 INNER JOIN

SELECT 
    a.column1, a.var1, b.vae2
FROM
    (SELECT 
        column1, COUNT(column1) AS var1
    FROM
        table1
    WHERE
        DATEDIFF(NOW(), createdAt) = 0
    GROUP BY column1) a
        INNER JOIN
    (SELECT 
        column1, COUNT(column1) AS var2
    FROM
        table2
    WHERE
        DATEDIFF(NOW(), createdAt) = 0
    GROUP BY column1) b ON a.column1 = b.column1;

【讨论】：

完美。谢谢

【解决方案2】：

SELECT *
FROM (
    select column1, count(column1) as var1 from table1 where  datediff(now(),createdAt) = 0 group by column1
) a 
JOIN (
    select column1, count(column1) as var2 from table2 where  datediff(now(),createdAt) = 0 group by column1
) b ON b.column1 = a.column1

【讨论】：