Working with join in sql?

Question

MySQL

There are two tables t1 and t2.
If I try to make a query:
select t1.* from t1 join t2 on t1.t2_id = t2.id
then those records that have a connection will get into the selection.
With a left join, all records will be included (with and without an existing connection).
How can I find those records that have no connection?

Answer 1

It sounds like a very bad idea.. Can you specify the task?

Answer 2

select t1.* from t1 left join t2 on t1.t2_id = t2.id where t2.id is null