MySQL 教程
/ HAVING
HAVING
MySQL HAVING 子句
HAVING 子句已添加到 SQL，因?yàn)?WHERE 關(guān)鍵字不能與聚合函數(shù)一起使用。
HAVING 語(yǔ)法
SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)HAVING conditionORDER BY
column_name(s);演示數(shù)據(jù)庫(kù)
以下是 Northwind 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 |
MySQL HAVING 示例
以下 SQL 語(yǔ)句列出了每個(gè)地區(qū)的客戶數(shù)量。 僅包括擁有 5 個(gè)以上客戶的地區(qū):
實(shí)例
SELECT COUNT(CustomerID), CountryFROM CustomersGROUP BY Country
HAVING COUNT(CustomerID) > 5;
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以下 SQL 語(yǔ)句列出了每個(gè)地區(qū)的客戶數(shù)量，從高到低排序（僅包括客戶超過(guò) 5 個(gè)的地區(qū)）:
實(shí)例
SELECT COUNT(CustomerID), CountryFROM CustomersGROUP BY CountryHAVING COUNT(CustomerID)
> 5
ORDER BY COUNT(CustomerID) DESC;
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演示數(shù)據(jù)庫(kù)
以下是 Northwind 示例數(shù)據(jù)庫(kù)中"Orders"表的選擇:
| 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 |
以及從"Employees"表中選擇的內(nèi)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.... |
更多 HAVING 示例
以下 SQL 語(yǔ)句列出了注冊(cè)超過(guò) 10 個(gè)訂單的員工:
實(shí)例
SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrdersFROM
(OrdersINNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID)
GROUP BY LastNameHAVING COUNT(Orders.OrderID) > 10;
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以下 SQL 語(yǔ)句列出員工"Davolio"或"Fuller"是否已注冊(cè)超過(guò) 25 個(gè)訂單:
實(shí)例
SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrdersFROM Orders
INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
WHERE LastName = 'Davolio' OR LastName = 'Fuller'GROUP BY LastNameHAVING
COUNT(Orders.OrderID) > 25;
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