[LeetCode/SQL] 1795. Rearrange Products Table

[LeetCode/SQL]

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📌 1795. Rearrange Products Table

문제

풀이

- product_id별 store1,2,3에서 null값을 제외하고,
열 변경
==> UNION 사용 

방법

SELECT product_id
      ,'store1' AS store
      ,store1 AS price
FROM Products
WHERE store1 IS NOT NULL
UNION
SELECT product_id
      ,'store2' AS store
      ,store2 AS price
FROM Products
WHERE store2 IS NOT NULL
UNION
SELECT product_id
      ,'store3' AS store
      ,store3 AS price
FROM Products
WHERE store3 IS NOT NULL