Execute only one exists in SQL

Question

I'm creating a report with iReport over an Oracle DB. I have to select some values depending on a condition like this:

AND EXISTS (SELECT 1 FROM TABLE_1 WHERE x = y)  
OR EXISTS (SELECT 1 FROM TABLE_2 WHERE z = y) 

is it possible to execute the second EXISTS only if the first is false?

Answer 1

Try to use your conditions in brackets:

AND (
        EXISTS (SELECT 1 FROM TABLE_1 WHERE x = y)  
     OR EXISTS (SELECT 1 FROM TABLE_2 WHERE z = y)
    )