Implementation method of MySQL query result taking intersection

  • 2020-05-14 05:07:46
  • OfStack

1
How do you implement the following SQL queries in MySQL
(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')
Please give me your advice. Thank you in advance
Solution:
Take the intersection
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.
Intersection:
SELECT * FROM table1 AS a JOIN table2 AS b ON a.name =b.name
For example:
Table a:
FieldA
001
002
003
Table b:
FieldA
001
002
003
004
How can I get the following result set, the intersection of rows of table A and B
FieldA
001
002
003
Answer: select a.FieldA from a inner join b on a. FieldA= b. FieldA
Difference set:
NOT IN stands for difference set
SELECT * FROM table1 WHERE name NOT IN (SELECT name FROM table2)

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