Question

我想在以下查询中添加某种“容差”。这意味着，我可以指定一个值，该值表示四个（子）选择返回行中的多少个＆gt;所以如果这个值是2，我只想加入这两个表。有没有办法实现这一点？

SELECT distinct(user_id) FROM 

(SELECT user_id FROM table1 WHERE ...) as t1
INNER JOIN
(SELECT user_id FROM table1 WHERE ...) as t2
ON t1.user_id=t2.user_id
INNER JOIN
(SELECT user_id FROM table1 WHERE ...) as t3
ON t1.user_id=t3.user_id
INNER JOIN
(SELECT user_id FROM table1 WHERE ...) as t4
ON t1.user_id=t4.user_id

修改每个子查询的可能结果如下：

t1 t2 t3 t4
 0  0  0
 1  1  1  1
 2  2  2  2
 3        3

如果所有这些子结果都加入，则会导致：1,2。如果我添加公差因子为1，我希望我的结果为0,1,2因为只缺少一个“0”。如果因子为2，则结果为0,1,2,3，因为缺少两个“3”和一个“0”。我希望这更清楚。

Answer 1

如果我理解了您的问题，您可以在子选择中添加变量并在以下后过滤：

SELECT distinct(user_id) FROM     
(SELECT user_id, 1 as table_from FROM table1 WHERE ...) as t1
INNER JOIN
(SELECT user_id, 2 as table_from FROM table1 WHERE ...) as t2
ON t1.user_id=t2.user_id
INNER JOIN
(SELECT user_id, 3 as table_from FROM table1 WHERE ...) as t3
ON t1.user_id=t3.user_id
INNER JOIN
(SELECT user_id, 4 as table_from FROM table1 WHERE ...) as t4
ON t1.user_id=t4.user_id
WHERE table_from <= 2;

Answer 2

解决方案是联合所有子选择并计算它们如下：

SELECT distinct(user_id), sum(t) as tolerance FROM (

SELECT user_id, 1 as t FROM table1 WHERE ... GROUP BY...
UNION ALL
SELECT user_id, 1 as t FROM table1 WHERE ... GROUP BY...
UNION ALL
SELECT user_id, 1 as t FROM table1 WHERE ... GROUP BY...
UNION ALL
SELECT user_id, 1 as t FROM table1 WHERE ... GROUP BY...

) as x GROUP BY ... HAVING tolerance <= 2

然后你可以指定应该返回多少个子选项（这里：2）。

MySQL加入“容忍”

2 个答案: