Comment by adamzochowski

This depends on the join type.

    select ...
    from table1 
        left join mytable2 on ... 
    where ..

If you move contents of where clause to the join/on clause, you will change meaning of the query.

If someone has a complex query or complex performance, they could do either subselects

    select ...
    from ( select ... from table1 where ... ) as table1_filtered
        inner join mytable2 on ... 

or CTEs

    with table1_filtered as ( select ... from table1 where ... ) 
    select ...
    from table1_filtered
        inner join mytable2 on ...