mysql - 将集合论思想转化为 SQL

Question

假设我有以下数据库表：

╔═════════════════╦════════════╗
║ ADVERTISEMENTID ║ CATEGORYID ║
╠═════════════════╬════════════╣
║               1 ║ A          ║
║               1 ║ C          ║
║               2 ║ A          ║
║               2 ║ B          ║
║               3 ║ A          ║
╚═════════════════╩════════════╝

给定作为参数传递的类别列表，假设A, C我只想查找仅属于这两个类别的广告，在上述情况下，只有广告1会匹配。

谁能帮我把它翻译成SQL？

Answer 1

select advertismentid
from the_table
where categoryid in ('A', 'C')
group by  advertismentid
having count(*) = 2;

SQLFiddle：http ://sqlfiddle.com/#!12/b94d6/1

这假定不能将相同的 categoryid 多次分配给相同的 advertismentid。它还将包括具有 A、C 和其他类别的广告。

如果您想要那些恰好具有A 类和 C 类的广告，您需要排除那些具有更多类别的广告：

select advertismentid
from the_table
where categoryid in ('A', 'C')
group by  advertismentid
having count(*) = 2;
intersect
select advertismentid
from the_table
group by advertismentid
having count(*) = 2;

SQLFiddle: http://sqlfiddle.com/#!12/8901c/4
The SQLFiddle also has another solution using except instead of intersect

If your DBMS is limited and you cannot use except or intersect, you can use this alternative:

select t1.advertismentid
from the_table t1
where t1.categoryid in ('A', 'C')
group by t1.advertismentid
having count(*) = 2
and count(*) = (select count(*) 
                from the_table t2
                where t2.advertismentid = t1.advertismentid)

Answer 2

SELECT DISTINCT advertisementid 
FROM tft t1
WHERE t1.categoryid IN ('A','C')
AND EXISTS (
  SELECT * FROM tft t2
  WHERE t2.advertisementid = t1.advertisementid
  AND t2.categoryid IN ('A','C')
  AND t2.categoryid <> t1.categoryid
  );

Answer 3

It seems I came late, but here is my solution anyway:

SELECT advertisement
FROM   advertisement_childcare_types t1
LEFT JOIN (
       SELECT childcare_types ct
       FROM   table_childcare_types tct
       WHERE  childcare_types IN (0, 1, 3)
          ) AS mytypes
ON     t1.childcare_types = mytypes.ct
GROUP BY advertisement
HAVING SUM(IF(mytypes.ct IS NULL, -1, 1)) = 3;

You can test in your sqlfiddle using this modified version:

SELECT advertisement
FROM   advertisement_childcare_types t1
LEFT JOIN (SELECT 0 as ct UNION SELECT 1 UNION SELECT 3) AS mytypes
ON     t1.childcare_types = mytypes.ct
GROUP BY advertisement
HAVING SUM(IF(mytypes.ct IS NULL, -1, 1)) = 3;