Applying conditional statement in Oracle DB

In the Oracle DB there are three tables, see below. Table: *'People'* Table: *'Dogs'* Table: *'Cats'* Here is a Fiddle with data to test : http://sqlfiddle.com/#!4/d7cb4 Depending on the result of a query from the *'People'* table, how can I proceed with a different query to request data further either from *'Dogs'* or *'Cats'*. Simply saying I need to execute a corresponding query depending on the answer of the initial/main query. Here is what I tried, (which obviously does not work): WITH CONDITION_CHECK AS ( SELECT ADORE FROM PEOPLE WHERE ADORE = 'dog' --here I will put my variable ) SELECT CASE WHEN CC.ADORE = 'dog' THEN (SELECT * FROM DOGS) WHEN CC.ADORE = 'cat' THEN (SELECT * FROM CATS) ELSE NULL END FROM CONDITION_CHECK AS CC What is the most common approach to set up a conditional statement in Oracle DB? And how can one execute it? I have seen the [IF-THEN-ELSE Statement](https://www.techonthenet.com/oracle/loops/if_then.php) , but I do not understand it much. ---------- **References:** - [Performing a query on a result from another query?](https://stackoverflow.com/questions/949465/performing-a-query-on-a-result-from-another-query) - [Using IF ELSE statement based on Count to execute different Insert statements](https://stackoverflow.com/questions/14072140/using-if-else-statement-based-on-count-to-execute-different-insert-statements) - [IF Condition Perform Query, Else Perform Other Query](https://stackoverflow.com/questions/17199604/if-condition-perform-query-else-perform-other-query)