SQL HAVING

وصف SQL HAVING

تمت إضافة التعبير HAVING إلى SQL لأنه لا يمكن استخدام الكلمة الأساسية WHERE مع الوظائف المجمعة.

يتم استخدام SQL HAVING لتصفية القيم حسب المجموعات التي تم إنشاؤها بواسطة عبارة GROUP BY.

HAVING بناء الجملة

SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition
ORDER BY column_name(s)

قاعدة البيانات التوضيحية

ما يلي هو نموذج من جدول "Customers" ("العملاء") لقاعدة البيانات "Northwind":

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

أمثلة SQL HAVING

يسرد استعلام SQL التالي عدد العملاء في كل بلد. يشمل فقط البلدان التي لديها أكثر من 5 عملاء:

Run SQLSELECT COUNT(CustomerID), Country 
FROM Customers 
GROUP BY Country 
HAVING COUNT(CustomerID) > 5

يسرد استعلام SQL التالي عدد العملاء في كل بلد، مرتبة من الأكبر إلى الأصغر (يشمل فقط البلدان التي لديها أكثر من 5 عملاء):

Run SQLSELECT COUNT(CustomerID), Country 
FROM Customers 
GROUP BY Country 
HAVING COUNT(CustomerID) > 5 
ORDER BY COUNT(CustomerID) DESC

قاعدة البيانات التوضيحية

دعونا نلقي نظرة على نموذج من الجدول "Orders" ("الطلبات"):

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

والعينة من الجدول "Employees" ("الموظفون"):

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.

المزيد من الأمثلة HAVING

يسرد استعلام SQL التالي الموظفين الذين سجلوا أكثر من 10 طلبات:

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

تعرض عبارة SQL التالية البيانات إذا قام موظفو "Davolio" أو "Fuller" بتسجيل أكثر من 25 طلبًا:

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