SQL

oracle case

SELECT product_id, product_type_id,
  CASE product_type_id
    WHEN 1 THEN 'Book'
    WHEN 2 THEN 'Video'
    WHEN 3 THEN 'DVD'
    WHEN 4 THEN 'CD'
    ELSE 'Magazine'
  END
FROM products;

select case when oracle

SELECT
	CASE COLUMN1 WHEN 'N' THEN
		CASE COLUMN2
			WHEN 1 THEN NVL(COLUMN3,COLUMN4)
			WHEN 2 THEN NVL(COLUMN3,COLUMN4) 
			WHEN 3 THEN NVL(COLUMN3,COLUMN4) 
			WHEN 4 THEN NVL(COLUMN3,COLUMN4) 
			WHEN 5 THEN NVL(COLUMN3,COLUMN4) 
			WHEN 6 THEN NVL(COLUMN3,COLUMN4)
		ELSE COLUMN5 END 
	ELSE COLUMN6 END
FROM TABLE_NAME