better approach: case or join

from id extracting name from several tables. which is generally the
better approach?

select case when tab_tla='usr' then (select name from users where ... )
case when tab_tla='con' then (select title from contents where
...)
end as name;

as versus

select name
from users
where tab_tla='usr' and ...
join
select title
from contents
where tab_tla='con' and ...

I assume the former since the optimizer does not examine whether the
entire where clause might be false before executing the query.

thanks,
chester

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