12/29 쿼리문 공부 중 | 복습 목록

HAVING

https://www.w3schools.com/sql/sql_having.asp

MAX, MIN

https://www.w3schools.com/sql/sql_min_max.asp

IN

https://www.w3schools.com/sql/sql_in.asp

JOINS

https://www.w3schools.com/sql/sql_join.asp

SELF JOIN

https://www.w3schools.com/sql/sql_join_self.asp

UNION

https://www.w3schools.com/sql/sql_union.asp

SELECT 'Customer' AS Type, ContactName, City, Country
FROM Customers
UNION
SELECT 'Supplier', ContactName, City, Country
FROM Suppliers;

GROUP BY

https://www.w3schools.com/sql/sql_groupby.asp

SELECT Shippers.ShipperName, COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders
LEFT JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID
GROUP BY ShipperName;

PARTITION BY

https://gent.tistory.com/442 -> 여기 정리 굿

SELECT empno
     , ename
     , job
     , sal
     , MAX(sal) OVER(PARTITION BY job)
  FROM emp
 WHERE job IN ('MANAGER', 'SALESMAN')
 ORDER BY job

SUM(1)과 SUM(*)의 차이

https://gent.tistory.com/457
SUM(1)과 COUNT() 사용했을 경우 데이터가 없을 때 SUM(1)은 NULL을 반환하고 COUNT()는 0을 반환한다.