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MySQL: Select sum or 0 if no records found

Question by Guest | 2015-11-04 at 23:40

I would like to read out the sum of the values from one of my columns out of my MySQL database. I am using the following query for this.

SELECT SUM(col) FROM tab WHERE ...

There is no problem with this approach whenever the query finds at least one record. In this case, the correct sum is the result.

Unfortunately, whenever no record is matching, the query is not working anymore. In this case, the result is always NULL. However, instead of NULL, I would like to have 0 as returned value. Is there any possibility to do that?

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You can, for example, use the function COALESCE or IFNULL to change your query. I will give you an example:

SELECT COALESCE(SUM(col), 0) FROM tab WHERE ...
SELECT IFNULL(SUM(col), 0) FROM tab WHERE ...

COALESCE is returning the first passed parameter that is not NULL. That means: If SUM(col) is NULL, 0 as the second parameter will be returned. IFNULL is working in a similar way. If the first parameter passed to IFNULL is NULL, the second parameter will be returned, otherwise the first.
2015-11-05 at 00:29

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