为同一列返回具有不同特定数据的行或使用 POSTGRESQL 返回 0 行

Question

I am in college learning SQL vis Postgresql. This is my first post here so if I'm not posting correctly, let me know. I have a question that has me stumped.

A bank setup with multiple users having multiple accounts at multiple branches in multiple cities. The question wants to find any users that have at least 1 account at every branch in a specific city.

There are 3 branches in Brooklyn. I need to find all user ID's that have at least one account in each branch.

If they do not have at least 1 account in each branch, it should not return anything for that user.

I don't know how to return multiple rows with different results from the same column and REQUIRE the specific branch names be present or return nothing at all. (userID = a on one row, b on another row, c on anther row or do not return userID at all.) I do not want the entire answer, I just need to know what function I can use to do this and maybe some general guidance on what to do.

I can provide the table information if needed.

Thank you.

Answer 1

I don't want the complete answer

Good and better to learn.

So I explain here how to do, just let me know what's not clear.

I need to find all user ID's that have at least one account in each branch.

We construst the sql in 3 times:

sql1: per City the name of branches

sql2: per ID & City the name of branches

sql3: ID from sql1 & sql2 whith same branches

Go ahead and ask when you need.

On clue is to be able to have one field with all the branches in order to be able to test it easily.

See the logic in comment and other answer to get the final solution.