Question

okay so i have one database with three columns: id, username, and rating.

The database would look like this:

 ------------ ------------ ------------ 
|     ID     |     NAME   |   RATING   |
 ------------ ------------ ------------
|     1      |   bc112    |      3     |
 ------------ ------------ ------------
|     2      |   cd111    |      1     |
 ------------ ------------ ------------
|     2      |   cd111    |      2     |
 ------------ ------------ ------------
|     2      |   cd111    |      6     |
 ------------ ------------ ------------

So basically where I am stuck is how do I get the average rating for each specific user?

I tried this:

SELECT ID, RATING
FROM THING
WHERE AVG(RATING) FOR ID < 3;

But the result is showing me nothing. What is wrong with the code?

Answer 1

By using AVG aggregate function, group by clause and having clause as follows:

SQL> with t1 (ID, NAME, RATING) as
  2  (
  3    select 1, 'bc112', 3  from dual union all
  4    select 2, 'cd111', 1  from dual union all
  5    select 2, 'cd111', 2  from dual union all
  6    select 2, 'cd111', 6  from dual
  7  )
  8  select ID
  9       , NAME
 10       , avg(rating)
 11    from t1
 12   group by id, name
 13   having avg(rating) > 2 
 14  ;

        ID NAME  AVG(RATING)
---------- ----- -----------
         1 bc112           3
         2 cd111           3