Trouble with GROUP BY CASE

Question

The following query gives the error \"#1241 - Operand should contain 1 column(s)\" because of the (Department_Code, Course_Code) line. When I replace that with just (Course

Answer 1

Had the same problem but found a simpler way which was to construct a helper field that can then be referenced in the GROUP BY. Or you can do the same conditional trick placing it in the GROUP BY so long as you Concat the fields.

SELECT *,

If( 'whatever field to check' = 2 , CONCAT(Department_Code,Course_Code), Course_Code) AS 'group1'

FROM Classes
GROUP BY group1