IDENTITY函数 -- 只能用在SELECT INTO语句中，用于在插入数据的时候模拟IDENTITY属性的作用生成自增长值。
SELECT IDENTITY(int, 1,1) AS ID_Num INTO NewTable FROM OldTable;
IDENT_INCR 函数 -- 返回表的自动增长值，比如我们希望每次增长1，那这个函数就会返回1.
USE AdventureWorks2012; GO SELECT TABLE_SCHEMA, TABLE_NAME, IDENT_INCR(TABLE_SCHEMA + ‘.‘ + TABLE_NAME) AS IDENT_INCR FROM INFORMATION_SCHEMA.TABLES WHERE IDENT_INCR(TABLE_SCHEMA + ‘.‘ + TABLE_NAME) IS NOT NULL;
IDENT_SEED 函数 -- 自动增长列的初始种子值
USE AdventureWorks2012; GO SELECT TABLE_SCHEMA, TABLE_NAME, IDENT_SEED(TABLE_SCHEMA + ‘.‘ + TABLE_NAME) AS IDENT_SEED FROM INFORMATION_SCHEMA.TABLES WHERE IDENT_SEED(TABLE_SCHEMA + ‘.‘ + TABLE_NAME) IS NOT NULL; GO
IDENT_CURRENT -- 表的IDENTITY列的当前自动增长值
USE AdventureWorks2012; GO SELECT TABLE_SCHEMA, TABLE_NAME, IDENT_CURRENT (TABLE_SCHEMA + ‘.‘ + TABLE_NAME) AS IDENT_SEED FROM INFORMATION_SCHEMA.TABLES WHERE IDENT_CURRENT (TABLE_SCHEMA + ‘.‘ + TABLE_NAME) IS NOT NULL; GO
SCOPE_IDENTITY() -- 当前模块内（存储过程）生成的最大自动增长值
@@IDENTITY -- 当前会话内生成的最大自动增长值
原文：http://www.cnblogs.com/jenrrychen/p/5979232.html