mysql - Forming Case statements in SQL -

mysql - Forming Case statements in SQL -

i need form case statements next queries:

select distinct t iwa b exists ( select * iwa t=320 , art=1234 ) , exists ( select * iwa t=450 , art=1234 , art=b.art ); select t iwa t=320 art=1234; select t iwa t=450 art=1234;

t column name, iwa table name , art input. should output above queries checked.

i can't understand trying achieve. maybe need this?

select t iwa (t=320 , art=1234) or (t=450 , art=1234)

mysql sql-server