SQL distinct count

Question

Hi..
Can anyone tell me how to do the SQL
SELECT EMPNO,DISTINCT(COUNT(SALARY))
FROM EMPLOYEE
Thanks in Advnace......
Rajeshwari

Answer 1

You need to count the distinct account_keys in the account table as an in-line view and join that to the product table. Something like:
SELECT p.product_key, p.name, a.cnt
FROM product p,
     (SELECT product_key, COUNT(DISTINCT account_key) cnt
      FROM account
      GROUP BY product_key) a
WHERE p.product_key = a.product_keyAlthough, your sample data gives odd results because there are two entries for p1 A and product p4 has two names D and B, although since it does not appear in accounts, it makes no differene in this particular case.
If you actually want to show all of the products from the product table and a zero count if they do not appear in accounts, then you need an outer join, something like:
SELECT p.product_key, p.name, NVL(a.cnt, 0) cnt
FROM product p
LEFT JOIN (SELECT product_key, COUNT(DISTINCT account_key) cnt
           FROM account
           GROUP BY product_key) a
   ON p.product_key = a.product_keyHTH
John