mysql - 匹配字段数（列）

Question

只是出于好奇，有没有一种方法可以让我获得 2 个或更多表中匹配数据的计数。如，如果我们得到以下 3 个表，

tbl_1-
ip  |isp    |infection
----------------------
1   |aaaa   |malware
2   |bbbb   |malware
3   |cccc   |ddos
3   |cccc   |trojan
4   |dddd   |ddos

tbl_2-
ip  |isp    |infection
----------------------
1   |aaaa   |malware
3   |cccc   |ddos
4   |dddd   |trojan
5   |eeee   |trojan
6   |ffff   |other

tbl_3-
ip  |isp    |infection
----------------------
1   |aaaa   |ddos
6   |ffff   |
2   |bbbb   |other

我能得出如下所示的答案吗？

Result-
ip  |isp    |infection  |Match Count
------------------------------------
1   |aaaa   |malware    |2      
1   |aaaa   |ddos       |1      
2   |bbbb   |malware    |1
2   |bbbb   |other      |1
3   |cccc   |ddos       |2
3   |cccc   |trojan     |1
4   |dddd   |ddos       |1
4   |dddd   |trojan     |1
5   |eeee   |trojan     |1
6   |ffff   |other      |1
6   |ffff   |           |1

谢谢 ：）

Answer 1

您需要为此使用UNION ALL（不仅是 UNION）以允许重复

SELECT ip, isp, infection, COUNT(*)
FROM 
(
SELECT ip, isp, infection FROM tbl_1
UNION ALL
SELECT ip, isp, infection FROM tbl_2
UNION ALL
SELECT  ip, isp, infection FROM tbl_3
) x
GROUP BY ip, isp, infection

SQLFiddle 演示

Answer 2

您应该对所有三个表执行 UNION ALL，然后按 ip、isp、感染列运行 GROUP BY。

SELECT ip, isp, infection, COUNT(*) 'Match Count'
FROM
(
    SELECT * FROM tbl_1
    UNION ALL
    SELECT * FROM tbl_2
    UNION ALL
    SELECT * FROM tbl_3
) AS A
GROUP BY ip, isp, infection

Answer 3

是的，您可以使用 COUNT() 函数 http://dev.mysql.com/doc/refman/5.1/en/group-by-functions.html#function_count