sql having用法与实例教程

sql having用法与实例教程HAVING子句是可选的，结合使用group by子句。它类似于Where子句，但经条款规定的限制，确定哪些记录后，将显示他们已进行分组。它通常都处于SQL语句的结束，一个HAVING子句的SQL语句可能会也可能不包括group by子句。对于拥有语法如下：SELECT column1, ... column_n, aggregate_function (expression) FROM table_name [WHERE condition] [GROUP BY column1, ... column_n] HAVING condition实例:Select Item, Sum(Price) as TotalSum From Antiques Group by Item Having Sum(Price)>57查询返回不同的项目和所谓'字段列表TotalSum'算数的古董结果总和供应每个项目。 HAVING子句将只返回那些超过57美元的金额与项目的结果。范例＃2Select SellerID, Count(*) as Number_of_Sellers From Antiques Where BuyerID=21 Group by SellerID Having Count(*)>1个例子显示了卖方的ID列表，以及它们的数量，但只有在有一个以上的BuyerID等于15卖方。例如＃3SELECT Item, COUNT(Item) AS Total, MAX(Price) AS MaxPrice FROM Antiques GROUP BY Item HAVING COUNT(Item) > 1 AND MAX(Price)