Question

I’m trying to select duplicates from this table:

snr zip
01 83
02 82
03 43
04 28

Expected result is just empty table. Cuz it got no duplicates.

I’ve tried with this query:

SELECT snr, zip
FROM student
GRUOP BY snr
HAVING  (COUNT(zip) > 1)

But it says that syntax is error, and that I’m trying to query an aggregate functions, etc..

Answer 1

It looks like you need to either remove zip from the SELECT columns, or else wrap it in an aggregate function, such as COUNT(zip):

SELECT   snr, COUNT(zip)
FROM     student
GROUP BY snr
HAVING   (COUNT(zip) > 1)

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Also check out @OMG Ponies’s answer for further suggestions.