db admins, I require your help!

My experience working with databases directly using SQL is rather limited, since I've mostly been using ORMs to cover all my needs as a frontend developer, but this time I need to use SQL to look up a token in tokens table that is using an id column of users table as its foreign key in which(inusers table) I only have access to the information stored in username column. I'm using PostgreSQL database.

Here's a visualization: very cool picture

Appreciate your help

  • 1
    Read about joins.
    – mustaccio
    Jul 3, 2022 at 12:44

2 Answers 2


The answer you came up with can work but is liable to error out should your subquery ever produce multiple results (though I'd assume unlikely) and likely is less performant than a more relational approach such as using a JOIN like mustaccio mentioned in the comments. You should definitely read up on them, which would allow you to produce a query like such:

SELECT token 
FROM tokens 
    ON tokens.id_ref = users.id
WHERE users.username = '<username>'

(I leave this answer here just for the context of J.D's solution, use JOINs)

Ok, so after fiddling with it for a bit, I found my solution:

SELECT token FROM tokens WHERE id_ref = (SELECT id FROM users WHERE username = '<username>');

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