SQL HAVING 子句


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

 HAVING子句已添加到SQL中,因为WHERE关键字不能用于聚合函数。

SQL HAVING 语法

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

演示数据库


 以下是罗斯文示例数据库中”Customers”表的选择:

CustomerIDCustomerNameContactNameAddressCityPostalCodeCountry
1

Alfreds FutterkisteMaria AndersObere Str. 57Berlin12209Germany
2Ana Trujillo Emparedados y heladosAna TrujilloAvda. de la Constitución 2222México D.F.05021Mexico
3Antonio Moreno TaqueríaAntonio MorenoMataderos 2312México D.F.05023Mexico
4

Around the HornThomas Hardy120 Hanover Sq.LondonWA1 1DPUK
5Berglunds snabbköpChristina BerglundBerguvsvägen 8LuleåS-958 22Sweden

SQL HAVING示例


 以下SQL语句列出了每个国家/地区的客户数量。只包括超过5位客户的国家/地区:

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;

 以下SQL语句列出每个国家的客户数量,从高到低排序(仅包括拥有超过5名客户的国家/地区):

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC;

演示数据库


 以下是罗斯文示例数据库中”Orders”表的一个选择:

OrderIDCustomerIDEmployeeIDOrderDateShipperID
102489051996-07-043
102498161996-07-051
102503441996-07-082

并从”Employees”表中选择:

EmployeeIDLastNameFirstNameBirthDatePhotoNotes
1DavolioNancy1968-12-08EmpID1.picEducation includes a BA….
2FullerAndrew1952-02-19EmpID2.picAndrew received his BTS….
3LeverlingJanet1963-08-30EmpID3.picJanet has a BS degree….

更多HAVING示例


 以下SQL语句列出已注册超过10个订单的员工:

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;

 以下SQL语句列出员工“Davolio”或“Fuller”是否已注册超过25个订单:

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;