Case Statement With Count Function

Question

How would one write a Case Statement with a count greater than one? The below is what I have so far: I'm receiving an invalid identifier.

Select *, CASE WHEN COUNT(X.id ) >1 THEN X 
  ELSE  isnull END AS testing 
 from TestTable

Answer 1

Thanks for the comments. I was able to work through my problem as I'm new to Oracle.

The correct statement would be:

Select *, CASE WHEN COUNT(X.id ) >1 THEN 'X' 
  ELSE '' END AS testing 
 from TestTable

Group by *

Answer 2

COUNT itself is an aggregate function that you have to use with GROUP BY. But you can also use it as an analytic function:

SELECT t.*, CASE WHEN COUNT(t.id) OVER(PARTITION BY ...) > 1 THEN 'X'
ELSE '' END AS testing
FROM TEST_TABLE