CODEWITHSUNDEEP
sqljoin
Zhengyi Zhang
Zhengyi Zhang

Reputation: 63

How to join more than 2 tables to get union the result?

the Venn show what I want&what I get

I have a SQL like this:


    SELECT 
           A.NAME,
           A.CODE,
           B.b_grade,C.c_grade 
      FROM A
     JOIN B ON B.NAME = A.NAME
     JOIN C ON C.NAME = A.NAME

I want to get the result like the Veen show. but the SQL's result give me another.

PS:the table B don’t have column “c_grade” ,so at the sql result ,for B ,the column “c_grade ” can be set zero

Upvotes: 0

Views: 88

Answers (3)

ammad khan
ammad khan

Reputation: 1154

Try this

SELECT * 
FROM tabA 
INNER JOIN tabB
      ON tabA.primaryKey=tabB.tabAId
INNER JOIN tabC
      ON tabA.primaryKey=tableC.tabAId

Upvotes: -1

ismetguzelgun
ismetguzelgun

Reputation: 1105

Below is all you need to do.

Set Operators

SELECT A.NAME, A.CODE, B.B_GRADE, NULL AS C_GRADE
  FROM A JOIN B ON B.NAME = A.NAME
UNION ALL
SELECT A.NAME, A.CODE, NULL AS B_GRADE, C.C_GRADE
  FROM A JOIN C ON C.NAME = A.NAME

Upvotes: 1

kutschkem
kutschkem

Reputation: 8163

You can left outer join, and then check whether any of the tables matched:

SELECT 
       A.NAME,
       A.CODE,
       B.*,C.*
  FROM A
 LEFT JOIN B ON B.NAME = A.NAME
 LEFT JOIN C ON C.NAME = A.NAME
 WHERE B.NAME != NULL OR C.NAME != NULL

Upvotes: 1

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