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SQL Basics in PostgreSQL

Introduction
UNION
INTERSECT
9. How INTERSECT works
EXCEPT

Instruction

Excellent. Here is another keyword: INTERSECT. Let's change our example a little bit:

SELECT year
FROM cycling
WHERE country = 'Germany'

INTERSECT

SELECT year
FROM skating
WHERE country = 'Germany';

Instead of UNION (or UNION ALL), we've put INTERSECT in there. What's the difference?

Well, UNION gave you all the results from the first query PLUS the results from the second query. INTERSECT, on the other hand, only shows the rows which belong to BOTH tables.

In this case, we would get the years when Germany got a medal in cycling AND speed skating at the same time.

The conditions here stay the same: the number of columns in both tables must be the same and the number or text values must match.

Exercise

Find names of each person who has medals in cycling and skating. Use an INTERSECT.

Stuck? Here's a hint!

Type:

SELECT person
FROM cycling

INTERSECT

SELECT person
FROM skating;