Question

I was looking up different ways to write a query, and I’m just wondering which way do you all think is better way to go with the following options:

SELECT a.salary 
  FROM emp a
  JOIN emp b ON a.salary < b.salary
 WHERE b.id = 200

or

SELECT salary 
  FROM emp
 WHERE salary < (SELECT salary 
                   FROM emp 
                  WHERE id = 200)

I did some execution times with about 300 records in the table, and they come out about the same, so this is really just more about preference and accepted standards. I personally like the 2nd way better (just easier to read to me). I have a feeling the 1st is standard though. What do you all think?

Answer 1

I don’t think there is a definite answer to this question as it’s really dependent on the context of the query itself & the RDMS.

So in your case, you’ve done the research with 300 records. How about 3,000,000? Does it make a difference?

Personally I like Joins over Sub-Queries if I can help it, but like I said, this is really determined on a case by case basis.