When query db should I check if data exists first then select it ?

I always just select data then check if returned data is null or not, but I wonder if that is a good way.
But if I check for data exists then that will make 2 call to db, 1 for check and 1 for select, is this good ?
Or maybe I just overthinking it :).
What are your though about this ?

Thank you

Comments

[Adrian B.G.]

Depending on the storage and the query, most likely you will end up doing the same expensive operation, twice (network call + disk access). This optimization is done at the database level (with caching, indexing), the user (who makes the query) should not deal with it, exceptions occurs of course.

[Molly Struve (she/her)]

I actually wrote a post that talks about tradeoffs of making lots of database hits even if they are simple. You might find it helpful!

In your scenario it really depends.

• How many of these selects are you making?
  • If you are making millions then it might not be worth it to double up the hits.
• How big is the expected data set you are going to get back?
  • If you have a large dataset coming back then it might be worth it to do the exists. If the dataset is small then it is probably not worth it.