How to join two tables by multiple columns in SQL

Question

I have two tables named Evaluation and Value  In both tables  there are four columns  But three of the four are the same  In other words  they both have the CaseNum  FileNum  ActivityNum columns  In addition to those  the Evaluation table has the Grade column  and the Value table has the Score column  I want to merge the two into one table  joining by CaseNum  FileNum  and ActivityNum  so I have a new table of five columns  including Value and Score  Can I use INNER JOIN multiple times to do this

User · Answer

You would basically want something along the lines of   SELECT e    v Score   FROM Evaluation e LEFT JOIN Value v ON v CaseNum   e CaseNum AND v FileNum   e FileNum AND v ActivityNum   e ActivityNum

User · Answer

You should only need to do a single join   SELECT e Grade  v Score  e CaseNum  e FileNum  e ActivityNum FROM Evaluation e INNER JOIN Value v ON e CaseNum   v CaseNum AND e FileNum   v FileNum AND e ActivityNum   v ActivityNum

User · Answer

No  just include the different fields in the  ON  clause of 1 inner join statement   SELECT   from Evalulation e JOIN Value v ON e CaseNum   v CaseNum     AND e FileNum   v FileNum AND e ActivityNum   v ActivityNum

User · Answer

SELECT E CaseNum  E FileNum  E ActivityNum  E Grade  V Score FROM Evaluation E INNER JOIN Value V ON E CaseNum   V CaseNum AND E FileNum   V FileNum AND E ActivityNum   V ActivityNum

User · Answer

Yes  You can use Inner Join to join on multiple columns  SELECT E CaseNum  E FileNum  E ActivityNum  E Grade  V Score from Evaluation E INNER JOIN Value V ON E CaseNum   V CaseNum AND     E FileNum   V FileNum AND      E ActivityNum   V ActivityNum  Create table CREATE TABLE MyNewTab CaseNum int  FileNum int      ActivityNum int  Grade int  Score varchar 100    Insert values INSERT INTO MyNewTab Values CaseNum  FileNum  ActivityNum  Grade  Score  SELECT E CaseNum  E FileNum  E ActivityNum  E Grade  V Score from Evaluation E INNER JOIN Value V ON E CaseNum   V CaseNum AND     E FileNum   V FileNum AND      E ActivityNum   V ActivityNum

[mysql] How to join two tables by multiple columns in SQL?

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