SQL Having

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SQL HAVING 子句

在 SQL 中增加 HAVING 子句原因是，WHERE 关键字无法与聚合函数一起使用。

HAVING 子句可以让我们筛选分组后的各组数据。

HAVING 语法

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

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演示数据库

以下是从 Northwind 示例数据库的 "客户(Customers)" 表中查询的内容:

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.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	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

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SQL HAVING 实例

下面的 SQL 语句列出了每个国家/地区的客户数量。仅包括拥有5个以上客户的国家/地区:

实例

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5; 亲自试一试 »

以下 SQL 语句列出了每个国家/地区的客户数量，按从高到低的顺序排列（仅包括客户超过5个的国家/地区）:

实例

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC; 亲自试一试 »

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演示数据库

以下是从 "Orders" 表中选择的内容:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10248	90	5	1996-07-04	3
10249	81	6	1996-07-05	1
10250	34	4	1996-07-08	2

以及从 "Employees" 表中选择的内容:

EmployeeID	LastName	FirstName	BirthDate	Photo	Notes
1	Davolio	Nancy	1968-12-08	EmpID1.pic	Education includes a BA....
2	Fuller	Andrew	1952-02-19	EmpID2.pic	Andrew received his BTS....
3	Leverling	Janet	1963-08-30	EmpID3.pic	Janet has a BS degree....

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更多 HAVING 实例

以下SQL语句列出了已注册超过10个订单的员工:

实例

SELECT 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; 亲自试一试 »

以下SQL语句列出了员工 "Davolio" 或 "Fuller" 注册的订单是否超过25份:

实例

SELECT 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; 亲自试一试 »