MySQL HAVING 子句
MySQL HAVING 子句
MySQL 的 HAVING 子句是为了解决 WHERE 关键字无法与聚合函数一起使用的问题。
HAVING 语法
SELECT column_name(s)
FROM table_name
WHERE 条件
GROUP BY column_name(s)
HAVING condition
ORDER BY column_name(s);演示数据库
以下是 Northwind 示例数据库中“Customers”表的选段
| 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 |
MySQL HAVING 示例
以下 SQL 语句列出了每个国家/地区的客户数量。仅包含客户数超过 5 的国家/地区
示例
SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;
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以下 SQL 语句列出了每个国家/地区的客户数量，并按数量从高到低排序（仅包含客户数超过 5 的国家/地区）
示例
SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC;
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演示数据库
以下是 Northwind 示例数据库中“Orders”表的选段
| 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 |
并选择“Employees”表中的内容
| EmployeeID | LastName | FirstName | BirthDate | Photo | 注意 |
|---|---|---|---|---|---|
| 1 | Davolio | Nancy | 1968-12-08 | EmpID1.pic | 教育包括学士学位.... |
| 2 | Fuller | Andrew | 1952-02-19 | EmpID2.pic | Andrew 获得了 BTS 文凭.... |
| 3 | Leverling | Janet | 1963-08-30 | EmpID3.pic | Janet 拥有 BS 学位.... |
更多 HAVING 示例
以下 SQL 语句列出了注册了超过 10 个订单的员工
示例
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;
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以下 SQL 语句列出了员工“Davolio”或“Fuller”是否注册了超过 25 个订单
示例
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;
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