EXPERT RESPONSE
The students you're looking for are those that have all three rows in
the skills table. This requires analysis of a group of rows,
namely, the group of skill rows for each student. I would suggest to you that GROUP BY will be involved in the
solution.
SELECT std_id
FROM skills
WHERE skill IN ('Java','J2EE','Struts')
GROUP
BY std_id
HAVING COUNT(*) = 3
The WHERE clause ensures that only the three rows of skills
which we're interested in are retrieved from the table for
each student. The GROUP BY and HAVING clauses ensure that
all three were found.
How would you modify this solution to return, say,
all students who had at least two of those three skills?
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