Aggregate query.

Question

I want to find out difference between average earnings of department no 20 and 30.
Could anyone help me on this.

Answer 1

Hi,
Welcome to the forum!
You can do that without sub-queries, like this:
SELECT     AVG (CASE WHEN deptno = 20 THEN sal END)
      - AVG (CASE WHEN deptno = 30 THEN sal END)
                AS diff
FROM    scott.emp
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
Explain, using specific examples, how you get those results from that data.
If you're using commonly available tables (such as those in the scott schema) then you don't need to post sample data; just make it clear which table(s) you're using, and post the results and the explanation.
Always say what version of Oracle you're using (e.g. 11.2.0.2.0).
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