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SQL COALESCE Tutorial - Interactive Database Lesson

Lesson 31 of 31

Lessons

1. SELECT *
2. SELECT specific columns
3. WHERE ... Equals
4. WHERE ... Greater than
5. WHERE ... Greater than or equal
6. AND
7. OR
8. IN
9. DISTINCT
10. ORDER BY
11. LIMIT # of returned rows
12. COUNT(*)
13. COUNT(*) ... WHERE
14. SUM
15. AVG
16. MAX and MIN
17. GROUP BY
18. Nested queries
19. NULL
20. Date
21. Inner joins
22. Multiple joins
23. Joins with WHERE
24. Left joins
25. Table alias
26. Column alias
27. Self joins
28. LIKE
29. CASE
30. SUBSTR
31. COALESCE

COALESCE

Interactive SQL Tutorial

COALESCE takes a list of columns, and returns the value of the first column that is not null.

Suppose we wanted to find the most powerful weapon that a combatant has on hand. If value of gun is not null, that is the value returned. Otherwise, the value of sword is returned. Then you would run:
SELECT name, COALESCE(gun, sword) as weapon FROM fighters;

Suppose that a fighter’s tank could count as a weapon, and it would take precedence over the gun and the sword. Could you find each fighter’s weapon in that scenario?

SQL:

Query Result:

Available Tables:

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