SQL HAVING 子句
在 SQL 中增加 HAVING 子句原因是,WHERE 關(guān)鍵字無法與 Aggregate 函數(shù)一起使用。
HAVING子句已添加到SQL中,因?yàn)閃HERE關(guān)鍵字不能用于聚合函數(shù)。
SQL HAVING 語法
SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition
ORDER BY column_name(s);
演示數(shù)據(jù)庫(kù)
以下是羅斯文示例數(shù)據(jù)庫(kù)中"Customers"表的選擇:
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 snabbk?p | Christina Berglund | Berguvsv?gen 8 | Lule? | S-958 22 | Sweden |
SQL HAVING示例
以下SQL語句列出了每個(gè)國(guó)家/地區(qū)的客戶數(shù)量。只包括超過5位客戶的國(guó)家/地區(qū):
SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;
以下SQL語句列出每個(gè)國(guó)家的客戶數(shù)量,從高到低排序(僅包括擁有超過5名客戶的國(guó)家/地區(qū)):
SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC;
演示數(shù)據(jù)庫(kù)
以下是羅斯文示例數(shù)據(jù)庫(kù)中"Orders"表的一個(gè)選擇:
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 |
并從"Employees"表中選擇:
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.... |
更多HAVING示例
以下SQL語句列出已注冊(cè)超過10個(gè)訂單的員工:
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語句列出員工“Davolio”或“Fuller”是否已注冊(cè)超過25個(gè)訂單:
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;
更多建議: