Group By 多個分組集小結 --GROUPING SETS，GROUP BY CUBE，GROUP BY ROLLUP，GROUPING(),GROUPING_ID()

T-SQL 多個分組集共有三種 GROUPING SETS, CUBE, 以及ROLLUP， 其中 CUBE和ROLLUP可以當做是GROUPING SETS的簡寫版

示例數據庫下載：

http://files.cnblogs.com/files/haseo/TSQL2012.rar

GROUPING SETS

列出所有你設置的分組集

SELECT shipperid, YEAR(shippeddate) AS shipyear, COUNT(*) AS numorders
FROM Sales.Orders
GROUP BY GROUPING SETS
(
( shipperid, YEAR(shippeddate) ),
( shipperid ),
( YEAR(shippeddate) ),
( )
);

CUBE

列出所有可能的分組集

SELECT  shipperid ,
        YEAR(shippeddate) AS shipyear ,
        COUNT(*) AS numorders
FROM    Sales.Orders
GROUP BY CUBE(shipperid, YEAR(shippeddate));

1. ( shipperid, YEAR(shippeddate) )

2. ( shipperid )

3. ( YEAR(shippeddate) )

4. ( )

 

ROOLUP

以層級的方式列出分組集

SELECT  shipcountry ,
        shipregion ,
        shipcity ,
        COUNT(*) AS numorders
FROM    Sales.Orders
GROUP BY ROLLUP(shipcountry, shipregion, shipcity);

1. ( shipcountry, shipregion, shipcity )

2. ( shipcountry, shipregion )

3. ( shipcountry )

4. ( )

 

GROUPING（）
該函數用來區分帶入的元素是否屬於分組的一部分， 返回0表示屬於，1表示不屬於

SELECT  shipcountry ,
        GROUPING(shipcountry) AS grpcountry ,
        shipregion ,
        GROUPING(shipregion) AS grpcountry ,
        shipcity ,
        GROUPING(shipcity) AS grpcountry ,
        COUNT(*) AS numorders
FROM    Sales.Orders
GROUP BY ROLLUP(shipcountry, shipregion, shipcity);

 

GROUPING_ID（）

該函數返回分組列的位圖（學過二進制的小伙伴都懂的，8421...以此類推） ，如果是0則所有分組字段都是分組的一部分，如果某個分組字段不是分組集的一部分則返回對應數字（既相關二進制位置1），最后進行匯總。

如下代碼，如果shipcountry, shipregion, shipcity均是分組的一部分則返回0.  如果shipregion, shipcity 不在分組內，則是3 （0+2+1 ）

SELECT  GROUPING_ID(shipcountry, shipregion, shipcity) AS grp_id ,
        shipcountry ,
        shipregion ,
        shipcity ,
        COUNT(*) AS numorders
FROM    Sales.Orders
GROUP BY ROLLUP(shipcountry, shipregion, shipcity);