Select column value if not null else use another column value

Question

I have 2 columns in mysql table: a and b. a is allways string value and b is sometimes a string value and sometimes it is null.

How to construct a mysql SELECT so that the b would be taken if it is not null and a would be taken otherwise.

I tried to make some magic with concat and if...then with no success...

UPDATE - To extend my question, is there a function that would work like Ifnull but would work for null AND empty values?

Mark Byers · Accepted Answer · 2010-10-17 07:33:41Z

24

Use IFNULL(b, a).

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2.

This is a MySQL specific function. You can also use COALESCE in the same way. This will work in more databases but it has slightly worse performance in MySQL than IFNULL.

answered Oct 17, 2010 at 7:33

Mark Byers

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1 Comment

Jerry2 Over a year ago

Sorry I didn't find this function mysqlf.

Amber · Accepted Answer · 2010-10-17 07:34:24Z

3

IFNULL(b, a) ?

answered Oct 17, 2010 at 7:34

Amber

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Comments

Eyal Ch · Accepted Answer · 2014-05-05 08:12:06Z

3

IF(expr1,expr2,expr3)

If expr1 is TRUE (expr1 <> 0 and expr1 <> NULL) then IF() returns expr2; otherwise it returns expr3.

answered May 5, 2014 at 8:12

Eyal Ch

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