I have table called athletics, where in the columns are
By submitting your email address, you agree to receive emails regarding relevant topic offers from TechTarget and its partners. You can withdraw your consent at any time. Contact TechTarget at 275 Grove Street, Newton, MA.
student_id varchar(50) weight_lbs numeric height_cms numeric sport varchar(50)
c001 189 190 soccer c002 175 180 football c003 210 195 football c004 186 175 baseball
I want to find all athletes that are not football players but have weight_lbs greater than at least one football player. How do you find this using subqueries?
What you want is a correlated subquery that selects all the football players that have a weight less than the non-football athlete you're looking at ("looking at" is sort of a technical term I use to describe how a correlated subquery works) and if there are any, then the athlete you're looking at is selected --
select * from athletics X where sport <> 'football' and exists ( select 1 from athletics where sport = 'football' and weight_lbs < X.weight_lbs )
The X is the correlation variable that ties the weight comparison in the subquery to the particular row being examined by the outer query. The subquery selects 1 because it doesn't matter what it selects; what matters is whether any row satisfies the subbquery condition, and therefore makes the EXISTS condition of the outer query true. I'm not really sure what is most efficient -- select 1, select *, or select null (see How does WHERE EXISTS ( SELECT NULL... ) work?). I suppose a good optimizer will ignore the select list in the subquery anyway.
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.