[HackerRank][SQL(Oracle)] Ollivander's Inventory

 

※  The following tables contain data on the wands in Ollivander's inventory:

• Wands: The id is the id of the wand, code is the code of the wand, coins_needed is the total number of gold galleons needed to buy the wand, and power denotes the quality of the wand (the higher the power, the better the wand is).
  
• Wands_Property: The code is the code of the wand, age is the age of the wand, and is_evil denotes whether the wand is good for the dark arts. If the value of is_evil is 0, it means that the wand is not evil. The mapping between code and age is one-one, meaning that if there are two pairs, (code1, age1)  and (code2, age2), then code1 ≠ code2 and age1 ≠ age2.
  

 

■  [Basic Join]  Ollivander's Inventory

https://www.hackerrank.com/challenges/harry-potter-and-wands/problem?isFullScreen=true 

Q.

Harry Potter and his friends are at Ollivander's with Ron, finally replacing Charlie's old broken wand.
Hermione decides the best way to choose is by determining the minimum number of gold galleons needed to buy each non-evil wand of high power and age. Write a query to print the id, age, coins_needed, and power of the wands that Ron's interested in, sorted in order of descending power. If more than one wand has same power, sort the result in order of descending age.

A.

WITH WWP AS (
	SELECT 	ID, W.CODE AS CODE, COINS_NEEDED, POWER, AGE, IS_EVIL
	FROM 	WANDS W, WANDS_PROPERTY WP
	WHERE 	W.CODE = WP.CODE
)
SELECT 		ID, G_AGE, MIN_COINS_NEEDED, G_POWER
FROM 		WWP JOIN (
				SELECT 		AGE AS G_AGE, POWER AS G_POWER, MIN(COINS_NEEDED) AS MIN_COINS_NEEDED
				FROM 		WWP
				WHERE 		IS_EVIL = 0
				GROUP BY 	AGE, POWER
			) WWP_FL 
			ON 	WWP.AGE = WWP_FL.G_AGE AND 
				WWP.POWER = WWP_FL.G_POWER AND 
				WWP.COINS_NEEDED = WWP_FL.MIN_COINS_NEEDED
ORDER BY 	G_POWER DESC, G_AGE DESC;

SELECT		ID, G_AGE, MIN_COINS_NEEDED, G_POWER
FROM		WANDS W JOIN (
				SELECT		W.CODE, AGE AS G_AGE, POWER AS G_POWER, MIN(COINS_NEEDED) AS MIN_COINS_NEEDED
				FROM		WANDS W JOIN WANDS_PROPERTY WP ON W.CODE = WP.CODE
				WHERE		IS_EVIL = 0
				GROUP BY	W.CODE, AGE, POWER
			) WWP_FL 
			ON	W.CODE = WWP_FL.CODE AND 
				W.POWER = WWP_FL.G_POWER AND 
				W.COINS_NEEDED = WWP_FL.MIN_COINS_NEEDED
ORDER BY	G_POWER DESC, G_AGE DESC;