SQL SERVER 分組組合GROUPING SETS

1、分組匯總--概述

SQL SERVER增強了GROUP BY的功能，GROUPING SETS 子句允許你指定多個GROUP BY選項，可以通過一條SELECT語句實現復雜繁瑣的多條SELECT語句的查詢，並且更加的高效。

GROUPING SETS 的 GROUP BY 子句可以生成一個等效於由多個簡單 GROUP BY 子句的 UNION ALL 生成的結果集。

GROUPING SETS 可以生成等效於由簡單 GROUP BY、ROLLUP 或 CUBE 操作生成的結果。

GROUPING SETS、ROLLUP 或CUBE 的不同組合可以生成等效的結果集。

 

2、分組匯總--方法實例

SQL SERVER增強了WITH ROLLUP 能很方便的對同一個結果及進行匯總

下面通過實例說明GROUP BY、GROUPING SETS、WITH ROLLUP的用法和區別：

SQL 使用 ROLLUP 匯總數據

（1）、 准備基礎數據

CREATE TABLE #TBLPOPULATION
    (
      COUN NVARCHAR (100) ,--國家
      PROV NVARCHAR (100) ,--省份
      CITY NVARCHAR (100) ,--城市
      POPU INT --人口數量（百萬）
    );
DELETE  FROM #TBLPOPULATION;
INSERT  INTO #TBLPOPULATION VALUES  ( '中國', '河南', '鄭州', 9 );
INSERT  INTO #TBLPOPULATION VALUES  ( '中國', '河南', '許昌', 2 );
INSERT  INTO #TBLPOPULATION VALUES  ( '中國', '河北', '石家庄', 6 );
INSERT  INTO #TBLPOPULATION VALUES  ( '中國', '河北', '滄州', 2 );
GO
SELECT * FROM  #TBLPOPULATION

（2）、GROUP BY分組

--2.1常用分組方法（單分組）
SELECT COUN ,PROV ,SUM(POPU) AS POPU 
FROM #TBLPOPULATION
GROUP BY COUN, PROV
ORDER BY COUN, PROV

（3）GROUPING SETS分組

--3.1分別多組合並后UNION
SELECT COUN ,PROV ,SUM(POPU) AS POPU  
FROM #TBLPOPULATION
GROUP BY GROUPING SETS(COUN ,PROV)
ORDER BY COUN, PROV

--3.2分別多組多級合並后UNION--等價於ROLLUP,但比ROLLUP少一行合計
SELECT COUN ,ISNULL(PROV,'合計') AS PROV,SUM( POPU ) AS POPU 
FROM #TBLPOPULATION
GROUP BY GROUPING SETS(
(COUN),
(COUN, PROV)
)
ORDER BY COUN, PROV

--3.3分別多組多級合並后UNION--等價於ROLLUP,但比ROLLUP少一行合計
SELECT ISNULL (COUN, '合計') AS COUN,ISNULL( PROV,'合計' ) AS PROV,ISNULL( CITY,'合計' ) AS CITY,SUM( POPU ) AS POPU  
FROM #TBLPOPULATION
GROUP BY GROUPING SETS(
(COUN),
(COUN, PROV),
(COUN, PROV,CITY )
)
ORDER BY COUN, PROV ,CITY

 

  （4）WITH ROLLUP匯總

--ROLLUP 匯總數據（比GROUPING SETS 多一合計）
SELECT  ISNULL (COUN, '合計') AS COUN,ISNULL( PROV,'合計' ) AS PROV,ISNULL( CITY,'合計' ) AS CITY,SUM( POPU ) AS POPU
FROM    #TBLPOPULATION
GROUP BY COUN, PROV, CITY
WITH ROLLUP;

--另外寫法，結果於上相同
SELECT   CASE WHEN ( GROUPING( COUN) = 1 ) THEN N'合計' ELSE ISNULL (COUN, 'UNKNOWN') END AS COUN ,
       CASE WHEN ( GROUPING (PROV) = 1 ) THEN N'合計' ELSE ISNULL (PROV, 'UNKNOWN') END AS PROV ,
       CASE WHEN ( GROUPING (CITY) = 1 ) THEN N'合計' ELSE ISNULL (CITY, 'UNKNOWN') END AS CITY ,
       SUM(POPU ) AS POPU
FROM    #TBLPOPULATION
GROUP BY COUN, PROV, CITY
WITH ROLLUP;

 

 
DROP TABLE #TBLPOPULATION;