Relationship with join and select


I am very confused and frustrated here. What relationship does the columns in SELECT have with the actual JOIN query.

Ive got these three tables in my SELECT
dbUsers., dbPosts., dbKarma.*

but when I add a fourth table
dbUsers., dbPosts., dbKarma., dbPosts_share.

the whole query stops outputting results.

What relationship does the SELECT have with the JOIN query?
Why would this effect the query?
As far as I know, SELECT is for the actual output in the loop?

most likely because of either (1) a syntax error, or (2) an implicit cross join which returns a bazillion rows, and the query never finishes executing

it determines which column(s) are to be returned from the join

it wouldn’t

there is no such thing as a loop in mysql, but i think you have the right idea, the SELECT determines which columns are to be returned


What would happen if I added a table that is not in the join?
Is it expected to work?

I just did an SQL query in PhpMyAdmin with an additional table in the SELECT which is in my join query but I get an error saying “unknown table” why is this happening?

Can you post the structure of the tables concerned and the query that you’ve got so far?

without seeing the query, and without knowing which tables you actually have, i would only be guessing

if you want help, you have to give us more to go on…