Linux中offset函数,介绍SQl server 2012的新分析函数--Offset Functions

Window offset 函数包括两类，一类是计算相对于当前行的偏移位置，一类则是相对于window frame的起点或是终点。

第一类包括 LAG和LEAD这两个函数，第二类包括FIRST_VALUE, LAST_VALUE和 NTH_VALUE,在SQL server 2012中没有实现NTH_VALUE。

Example for  LAG and LEAD:

SELECT custid, orderdate, orderid, val,

LAG(val) OVER(PARTITION BY custid ORDER BY orderdate, orderid) AS prevval,

LEAD(val) OVER(PARTITION BY custid

ORDER BY orderdate, orderid) AS nextval

FROM Sales.OrderValues;

Result:

example for FIRST_VALUE, LAST_VALUE:

SELECT custid, orderdate, orderid, val,

FIRST_VALUE(val) OVER(PARTITION BY custid

ORDER BY orderdate, orderid) AS val_firstorder,

LAST_VALUE(val) OVER(PARTITION BY custid

ORDER BY orderdate, orderid

ROWS BETWEEN CURRENT ROW

AND UNBOUNDED FOLLOWING) AS val_lastorder

FROM Sales.OrderValues

order by custid,val

Result：

这个结果很好体会，因此不赘述