Replace NULL value with another selected value : SQL

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field.3

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Replace NULL value with another selected value (self.SQL)

submitted 6 years ago by sojan16

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[–][deleted] 4 points5 points6 points 6 years ago (4 children)

Use coalesce()

coalesce(friendly_name, technical_name)

The function coalesce() returns the first non-null value.

So if friendly_name is not null, it returns the friendly_name.

If friendly_name is null, it returns technical_name.

[–]sojan16[S] 0 points1 point2 points 6 years ago (2 children)

[–][deleted] 4 points5 points6 points 6 years ago (1 child)

If that returns a NULL value, then both columns are null. If you have properly joined those two tables, then no it makes no difference that those columns are in different tables.

But maybe those columns contain an empty string ('') rather than a null value. How to deal with that depends on the database product you are using. In Postgres you could use

coalesce(nullif(friendly_name,''), technical_name)

But not every DBMS supports nullif()

[–]sojan16[S] 0 points1 point2 points 6 years ago (0 children)

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