SQL 查看“ANY”行是否符合条件

Question

given the following SQL in Postgres, I want to see if any row matches the criteria and not interested in what rows match. eg in this case, (if i have any perishable stock)

The only way i have achieved this is use the limit clause but its very slow (there is >100,000,000 records)

select is_perishable
from stock
where is_perishable = true
limit 1;

Is there a quicker, more eloquent method in achieving this?

Answer 1

You could try EXISTS:

SELECT EXISTS(
  select null from stock where is_perishable = true
)

How much faster it'll be, if at all, I've no idea, but it ought to be optimized to quit early upon assessing the presence of a record.. Though so would a limit query... If it's no different, post the query plan

Answer 2

this might be a little bit faster:

select 1
from stock
where is_perishable = true
limit 1;

nevertheless it can be slow if there is no row with is_perishable = true. here a proper index can be helpful.