On Sunday, January 15, 2017, Hursh Jain <
hurshj@gmail.com> wrote:
SELECT * from property
WHERE pid in (
SELECT pid FROM reward WHERE reward_type = 'DAILYPROMO_WIN')
;
And this also runs (again taking a long time) but without any errors. How can this be ? (there is no pid in the reward table, so why does the
subquery not throw an error)?
The "pid" column is the one from the outer query property table - this is a correlated subquery that you've written.
As long as one record with that reward_type exists your query devolves to "where true" thus making indexes useless and returning every row in property.
David J.
