Question

I have a MySQL table with a structure like the following:

I’m looking for a select statement which will concatenate the last four fields as follows:

ID    Source
1     Search engine
2     Email
3     Coupon mailout
4     Relative of owner

I can think of a way to do this by using subqueries to choose the relevant fields to concatenate based on Type, nested subqueries to select values that are not NULL or ‘Other’, followed by JOINs, CONCAT()s and a UNION, but that seems a very complicated approach to the problem.

Am I overthinking this? Is there a simpler way?

Answer 1

If you can’t fix your data, you can simply use IF() function. In my example, I’m using simple column names to make it a bit clearer:

mysql> SELECT IF(c1 IS NOT NULL AND c1 != 'Other', c1,
        IF(c2 IS NOT NULL AND c2 != 'Other', c2,
        IF(c3 IS NOT NULL AND c3 != 'Other', c3, c4))) FROM t1;

The above was tested.

You could make a Stored Function out of it if you need to use it often.

But, if you can, fix the table structure?