Sql 简明教程

SQL - Aggregate Functions

一般来说，聚合是将一组对象作为一个整体联系在一起进行考虑。SQL 提供了一组聚合函数，对数据表的列的所有实体执行操作，并将其视为一个单元。以下是 SQL 聚合函数−

In general, aggregation is a consideration of a collection of objects that are bound together as a single entity. SQL provides a set of aggregate functions that perform operations on all the entities of the column of a table considering them as a single unit. Following are the SQL aggregate functions −

Sr.No.	Function & Description
1	APPROX_COUNT_DISTINCT()Returns the approximate number of rows with distinct expression values.
3	CHECKSUM_AGG()Returns the checksum value.
4	COUNT_BIG()Returns the count of the number of items or rows selected by the select statement.
6	GROUPING()Returns whether the specified column expression in a group by list is aggregate or not.
7	GROUPING_ID()Returns the level of grouping.
10	STDEV()Returns the statistical standard deviation of the fields (numerical values) in a particular column.
11	STDEVP()Returns the population standard deviation for the fields (numerical values) in a particular column.
13	VAR()Returns the statistical standard variance of the fields (numerical values) in a particular column.
14	VARP()Returns the population standard variance of the fields (numerical values) in a particular column.