CASE SQL statement

Question

I am curious if any one can tell me what I am doing wrong, or point me in the right direction. If someone can give me a hand, I would be thankful.

Here is the question: Using the weblog table in your database create a query that will Group the IP addresses and display a sum of the number of requests by each IP address that had a return code (retcode) of greater than 300 order this query by the retcode field in descending order.

Here is what I have so far:

SELECT COUNT(ipno) AS Number_of_Requests, retcode
FROM WebLog
GROUP BY ipno
HAVING retcode > 300
ORDER BY retcode DESC

Answer 1

The question is basically "wrong". The problem is that it is asking for results at the ip level and then asking for you to order by the return code. But a given IP could have more than one return code meeting the criteria.

One valid interpretation is that it really means "group by ip and retcode":

SELECT ipno, retcode, COUNT(ipno) AS Number_of_Requests
FROM WebLog
WHERE retcode) > 300
GROUP BY ipno
ORDER BY retcode DESC;

Another valid interpretation is that it means to order by the maximum retcode for each IP:

SELECT ipno, COUNT(ipno) AS Number_of_Requests
FROM WebLog
WHERE retcode > 300
GROUP BY ipno
ORDER BY MAX(retcode) DESC;

For this query, I would include GROUP_CONCAT(DISTINCT retcode) to see a list of such codes.

To be honest, I suspect the write of the question intended for the ORDER BY to be by the number of log entries, and the phrasing just came out wrong.

Answer 2

You need to move the filter clause to where . Also, it doesn't make sense to sort by retcode when you are grouping by IP.

If you really want to do that, use an aggregate function on retcode (say max ):

SELECT ipno, COUNT(ipno) AS Number_of_Requests, max(retcode)
FROM WebLog
where retcode > 300
GROUP BY ipno
ORDER BY max(retcode) DESC