SELECT CASE col1	WHEN 'agree' THEN 'Ok'	WHEN 'disagree' THEN 'Ko' ELSE CASE WHEN col2 >= 1 THEN 'Ko' ELSE 'Maybe' END
END AS my_result
FROM table_name;

-- Case Eg.) to retrive the MAX value of a Field
-- if there are entries for the Field in table MAX value will be returned
-- But if there is no entries at all for the Field in tabel MAX will return
-- Null as the output. But Using Case When we can check it out return zero
-- or any other value if there is no enties for the Field in table..
SELECT
CASE -- Like Switch Case	WHEN -- First When condition	(MAX(BILLID) IS NULL) -- Condition	THEN 1 -- output (We can also add more When conditions like Above)
ELSE -- When WHEN Condition not Satisfied Below will be Executed.	(MAX(BILLID)) -- output
END
as MAXBILLID from DUAL;
-- Final Output
-- If there is no entry in the Field for the table
-- BILLID
-- 1
-- If there are entries MAX of that Field value from the table
-- BILLID
-- 10