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

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?

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;

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

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

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