WHERE 키워드를 집계 함수와 함께 사용할 수 없기 때문에 HAVING 표현식이 SQL에 추가되었습니다.
SQL HAVING은 GROUP BY 문으로 생성된 그룹별로 값을 필터링하는 데 사용됩니다.
SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition
ORDER BY column_name(s)
다음은 "Northwind" 데이터베이스의 "Customers"("고객") 테이블의 샘플입니다.
| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 1 | Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 5021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 5023 | Mexico |
| 4 | Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
| 5 | Berglunds snabbköp | Christina Berglund | Berguvsvägen 8 | Luleå | S-958 22 | Sweden |
다음 SQL 쿼리는 각 국가의 고객 수를 나열합니다. 고객이 5명 이상인 국가만 포함됩니다.
Run SQLSELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
다음 SQL 쿼리는 각 국가의 고객 수를 가장 큰 것부터 가장 작은 것 순으로 정렬하여 나열합니다(고객이 5명 이상인 국가만 포함).
Run SQLSELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC
"Orders"("주문") 테이블의 샘플을 살펴보겠습니다.
| ProductID | OrderID | CustomerID | EmployeeID | OrderDate | ShipperID |
|---|---|---|---|---|---|
| 1 | 10248 | 90 | 5 | 1996-07-04 | 3 |
| 2 | 10249 | 81 | 6 | 1996-07-05 | 1 |
| 3 | 10250 | 34 | 4 | 1996-07-08 | 2 |
| 4 | 10251 | 84 | 3 | 1996-07-08 | 1 |
| 5 | 10252 | 76 | 4 | 1996-07-09 | 2 |
그리고 "Employees"("Employees") 테이블의 샘플은 다음과 같습니다.
| EmployeeID | LastName | FirstName | BirthDate | Photo | Notes |
|---|---|---|---|---|---|
| 1 | Davolio | Nancy | 12/8/1968 | EmpID1.pic | Education includes a BA in psychology from Colorado State University. She also completed (The Art of the Cold Call). Nancy is a member of 'Toastmasters International'. |
| 2 | Fuller | Andrew | 2/19/1952 | EmpID2.pic | Andrew received his BTS commercial and a Ph.D. in international marketing from the University of Dallas. He is fluent in French and Italian and reads German. He joined the company as a sales representative, was promoted to sales manager and was then named vice president of sales. Andrew is a member of the Sales Management Roundtable, the Seattle Chamber of Commerce, and the Pacific Rim Importers Association. |
| 3 | Leverling | Janet | 8/30/1963 | EmpID3.pic | Janet has a BS degree in chemistry from Boston College). She has also completed a certificate program in food retailing management. Janet was hired as a sales associate and was promoted to sales representative. |
| 4 | Peacock | Margaret | 9/19/1958 | EmpID4.pic | Margaret holds a BA in English literature from Concordia College and an MA from the American Institute of Culinary Arts. She was temporarily assigned to the London office before returning to her permanent post in Seattle. |
| 5 | Buchanan | Steven | 3/4/1955 | EmpID5.pic | Steven Buchanan graduated from St. Andrews University, Scotland, with a BSC degree. Upon joining the company as a sales representative, he spent 6 months in an orientation program at the Seattle office and then returned to his permanent post in London, where he was promoted to sales manager. Mr. Buchanan has completed the courses 'Successful Telemarketing' and 'International Sales Management'. He is fluent in French. |
다음 SQL 쿼리는 10개 이상의 주문을 등록한 직원을 나열합니다.
Run SQLSELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders
FROM (Orders
INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID)
GROUP BY LastName
HAVING COUNT(Orders.OrderID) > 10
다음 SQL 문은 "Davolio" 또는 "Fuller" 직원이 25개 이상의 주문을 등록한 경우 데이터를 표시합니다.
Run SQLSELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders
FROM Orders
INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
WHERE LastName = 'Davolio' OR LastName = 'Fuller'
GROUP BY LastName
HAVING COUNT(Orders.OrderID) > 25