Question

所以这些表格是这样的：

表1：

facilities   emails
Fac 1        fac1@email.com
Fac 2        fac2@email.com
Fac 1 RE     fac1@email.com

表2：

facilities  emails
fac1        fac1@email.com
fac2        fac3@email.com

现在，在这两张桌子上，我试图弄清楚有多少设施在使用每个地址电子邮件。我有两个SQL查询就是这样：

SELECT ce.email, count(*)  
AS TOTAL_FACILITIES 
FROM table1 
AS ce 
GROUP BY ce.email
ORDER BY TOTAL_FACILITIES DESC

SELECT ca.emails, count(*)  
AS TOTAL_FACILITIES 
FROM table2 
AS ca 
GROUP BY ca.emails
ORDER BY TOTAL_FACILITIES DESC

这为我提供了每张桌子的不同电子邮件以及有多少设施使用它们。我现在尝试使用联接将其组合成一个单独的调用，但我似乎无法弄清楚如何使计数工作。

有什么建议吗？

Answer 1

您可能希望改为UNION。

SELECT ce.email, count(*) AS TOTAL_FACILITIES 
FROM table1 AS ce 
GROUP BY ce.email
UNION
SELECT ca.emails, count(*) AS TOTAL_FACILITIES 
FROM table2 AS ca 
GROUP BY ca.emails
ORDER BY TOTAL_FACILITIES DESC

更好的解决方案是在聚合之前联合它。

SELECT email, COUNT(*) AS TOTAL_FACILITIES
FROM (
    SELECT facilities, email
    FROM table1
    UNION ALL
    SELECT facilities, email
    FROM table2
)
GROUP BY email
ORDER BY TOTAL_FACILITIES DESC

Answer 2

我认为你正在寻找这样的东西：

SELECT A.emails, COUNT(*) as total_facilities
FROM
(SELECT * FROM table1 UNION ALL SELECT * FROM table2) A
GROUP BY A.emails
ORDER BY COUNT(*) DESC;

SQL在多个表中组合了两个选择

2 个答案: