Question

ques1. sql’s where clause cant be used with aggregate functions(sum,avg, max,min) ?

ques2. Considering a table named cust, containing columns: orderno, custid, cost

select * from cust having cost> avg(cost)

avg(cost) gives output 5695 therefore, 3 records should come in the output since they have cost greater than 5695. But only one is coming. On the other hand this query:

select * from cust having cost>(select avg(cost) from cust) gives correct output why?

Answer 1

1. No, use HAVING
2. Because MySQL doesn’t implement SQL properly and does an implied GROUP BY

3. Because that is almost a correct query (see 2). It should be

   select * from cust where cost>(select avg(cost) from cust)