返回一个参数值的集合，这些参数值投影自聚合相关的当前组分区。 聚合 GroupPartition 是基于组的聚合，没有基于集合的形式。
语法
GROUPPARTITION( [ALL|DISTINCT] expression )
论据
expression 任何实体 SQL 表达式。
注解
以下查询生成产品列表以及每个产品的订单行数量集合：
SELECT p, GroupPartition(ol.Quantity) FROM LOB.OrderLines AS ol
GROUP BY ol.Product AS p
以下两个查询在语义上相等：
SELECT p, Sum(GroupPartition(ol.Quantity)) FROM LOB.OrderLines AS ol
GROUP BY ol.Product AS p
SELECT p, Sum(ol.Quantity) FROM LOB.OrderLines AS ol
group by ol.Product as p
运算符 GROUPPARTITION 可以与用户定义的聚合函数结合使用。
GROUPPARTITION 是一个特殊的聚合运算符，用于保存对分组输入集的引用。 可以在 GROUP BY 所在的查询中的任何位置使用此引用。 例如：
SELECT p, GroupPartition(ol.Quantity) FROM LOB.OrderLines AS ol GROUP BY ol.Product AS p
使用常规 GROUP BY，分组的结果将隐藏。 只能在聚合函数中使用结果。 若要查看分组的结果，必须使用子查询关联分组的结果和输入集的结果。 下面两个查询是等效的：
SELECT p, (SELECT q FROM GroupPartition(ol.Quantity) AS q) FROM LOB.OrderLines AS ol GROUP BY ol.Product AS p
SELECT p, (SELECT ol.Quantity AS q FROM LOB.OrderLines AS ol2 WHERE ol2.Product = p) FROM LOB.OrderLines AS ol GROUP BY ol.Product AS p
如示例中所示，GROUPPARTITION 聚合运算符使在分组后更容易获取对输入集的引用。
使用参数时 expression ，GROUPPARTITION 运算符可以在运算符输入中指定任何实体 SQL 表达式。
例如，组分区的所有以下输入表达式都有效：
SELECT groupkey, GroupPartition(b) FROM {1,2,3} AS a INNER JOIN {4,5,6} AS b ON true GROUP BY a AS groupkey
SELECT groupkey, GroupPartition(1) FROM {1,2,3} AS a INNER JOIN {4,5,6} AS b ON true GROUP BY a AS groupkey
SELECT groupkey, GroupPartition(a + b) FROM {1,2,3} AS a INNER JOIN {4,5,6} AS b ON true GROUP BY a AS groupkey
SELECT groupkey, GroupPartition({a + b}) FROM {1,2,3} AS a INNER JOIN {4,5,6} AS b ON true GROUP BY a AS groupkey
SELECT groupkey, GroupPartition({42}) FROM {1,2,3} AS a INNER JOIN {4,5,6} AS b ON true GROUP BY a AS groupkey
SELECT groupkey, GroupPartition(b > a) FROM {1,2,3} AS a INNER JOIN {4,5,6} AS b ON true GROUP BY a AS groupkey
示例：
以下示例演示如何将 GROUPPARTITION 子句与 GROUP BY 子句一起使用。 GROUP BY 子句按实体分组SalesOrderHeader。Contact 然后，GROUPPARTITION 子句投影 TotalDue 每个组的属性，从而生成小数的集合。
USING Microsoft.Samples.Entity
Function MyAvg(dues Collection(Decimal)) AS
(
Avg(SELECT value due FROM dues AS due WHERE due > @price)
)
SELECT TOP(10) contactID, MyAvg(GroupPartition(order.TotalDue))
FROM AdventureWorksEntities.SalesOrderHeaders AS order
GROUP BY order.Contact.ContactID AS contactID;