MySQL查询结果取交集的实现方法
2020-11-09
来源：小奈知识网
MySQL中如何实现以下SQL查询
(SELECT S.Name
FROM STUDENT S, TRANSCRIPT T
WHERE S.StudId = T.StudId AND T.CrsCode = 'CS305')
INTERSECT
(SELECT S.Name
FROM STUDENT S, TRANSCRIPT T
WHERE S.StudId = T.StudId AND T.CrsCode = 'CS315')
请各位不吝赐教，小弟先谢过~
解：
取交集
select a.* from
(
SELECT S.Name
FROM STUDENT S, TRANSCRIPT T
WHERE S.StudId = T.StudId AND T.CrsCode = 'CS305'
) as a
cross join
(
SELECT S.Name
FROM STUDENT S, TRANSCRIPT T
WHERE S.StudId = T.StudId AND T.CrsCode = 'CS315'
) as b on a.Name = b.Name;
2.
SELECT * FROM (
SELECT DISTINCT col1 FROM t1 WHERE...
UNION ALL
SELECT DISTINCT col1 FROM t1 WHERE...
) AS tbl
GROUP BY tbl.col1 HAVING COUNT(*) = 2
3.
交集：
SELECT * FROM table1 AS a JOIN table2 AS b ON a.name =b.name
举例：
表a:
FieldA
001
002
003
表b:
FieldA
001
002
003
004
请教如何才能得出以下结果集，即表A, B行交集
FieldA
001
002
003
答案：select a.FieldA from a inner join b on a.FieldA=b.FieldA
差集：
NOT IN 表示差集
SELECT * FROM table1 WHERE name NOT IN (SELECT name FROM table2)
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