Question

I have the statement

SELECT COUNT(*) as num_requests, ip_address FROM requests
GROUP BY ip_address
ORDER BY num_requests DESC;

When I use the following clause WHERE num_requests = 3 I get a syntax error

SELECT COUNT(*) as num_requests, ip_address 
FROM requests
WHERE num_requests = 3
GROUP BY ip_address
ORDER BY num_requests DESC;

Unknown column ‘num_requests’ in ‘where clause’

Is there any way I can use this WHERE clause without writing a nested query or join statement on the entire result set returned by the above?

Answer 1

You need having 🙂

SELECT COUNT(*) as num_requests, ip_address FROM requests
GROUP BY ip_address
HAVING COUNT(*) = 3
ORDER BY num_requests DESC;

To add a note on why WHERE couldn’t be used but HAVING : with aggregates such as SUM, MIN,MAX,AVG,COUNT etc WHERE doen’t work. So you have to use the latter.