SQL 计算不同的集合，多次重用行

Question

我正在尝试编写一个查询或一组查询来计算跨越多行的唯一集，但行中的数据可能需要计算多次。

在以下集合中，我想要按年份分组的以下计数

Number of unique SID, Year, Flag1  //2013=2, 2014=2
Number of unique SID, Year, Flag2  //2013=1, 2014=0
Number of unique SID, Year, Flag3  //2013=1, 2014=2

然后我想做同样的事情，按年/月分组

Number of unique SID, Year, Month, Flag1  //2013-Jan=2, 2013-Feb=2, 2013-Mar=1, etc
Number of unique SID, Year, Month, Flag2  //2013-Jan=1, 2013-Feb=1, 2013-Mar=1, etc
Number of unique SID, Year, Month, Flag3, //2013-Jan=1, 2013-Feb=1, 2013-Mar=1, etc

数据集

SID    Year     Month     Flag1     Flag2     Flag3
--------------------------------------------------
1      2013     Jan         Y         Y         Y
1      2013     Feb         Y         Y         Y
1      2013     Mar         Y         Y         Y
1      2014     Jan         Y                   Y
1      2014     Feb         Y 
2      2013     Jan         Y 
2      2013     Feb         Y  
2      2014     Jan         Y                   Y      
2      2014     Feb         Y                   Y     

我可以对每个计数使用一个查询来做到这一点，但我真的很想将它合并到一个查询中。

我今年的多次统计如下：

select count(*) from 
( select distinct SID, Year, Flag1 from Table WHERE Year = '2013' ) as 2013Flag1

select count(*) from 
( select distinct SID, Year, Flag2 from Table WHERE Year = '2013' ) as 2013Flag2

select count(*) from 
( select distinct SID, Year, Flag1 from Table WHERE Year = '2014' ) as 2014Flag1

等等……

月份计数如下所示：

select count(*) from 
( select distinct SID, Year, Month, Flag1 from Table WHERE Year = '2013' and Month = 'Jan' ) as 2013JanFlag1

等等……

查询每个计数是否更容易做到这一点，还是我可以选择某种类型的笛卡尔积？任何想法都会很棒。这来自 Oracle 数据库。我相信它是10g版本。

Answer 1

 SELECT G.SID, G.YEAR, G.MONTH, G.FLAG, COUNT(*)
 FROM (
 SELECT Y.YEAR, Y.SID, Y.MONTH, 1 AS FLAG
 (SELECT DISTINCT SID, YEAR FROM TABLE) AS Y
 JOIN TABLE AS F
   ON F.YEAR = Y.YEAR
  AND F.FLAG1 = 'Y'
 UNION ALL
 SELECT Y.YEAR, Y.SID, Y.MONTH, 2 AS FLAG
 (SELECT DISTINCT SID, YEAR FROM TABLE) AS Y
 JOIN TABLE AS F
   ON F.YEAR = Y.YEAR
  AND F.FLAG2 = 'Y'
 UNION ALL
 SELECT Y.YEAR, Y.SID, Y.MONTH, 3 AS FLAG
 (SELECT DISTINCT SID, YEAR FROM TABLE) AS Y
 JOIN TABLE AS F
   ON F.YEAR = Y.YEAR
  AND F.FLAG3 = 'Y' ) AS G
  GROUP BY G.SID, G.YEAR, G.FLAG, G.MONTH
  ORDER BY G.SID, G.YEAR, G.FLAG, G.MONTH

Answer 2

我没有得到关于标志的逻辑，但也许 ROLLUP 或 CUBE 使查询更容易和更快。

以下语句是等价的：

SELECT COUNT(DISTINCT SID), YEAR, MONTH, flag1, flag2, flag3
FROM a_table
GROUP BY flag1, flag2, flag3, ROLLUP(YEAR, MONTH);

SELECT COUNT(DISTINCT SID), YEAR, MONTH, flag1, flag2, flag3
FROM a_table
GROUP BY flag1, flag2, flag3, YEAR, MONTH
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, NULL AS MONTH, flag1, flag2, flag3
FROM a_table
GROUP BY flag1, flag2, flag3, YEAR
UNION ALL
SELECT COUNT(DISTINCT SID), NULL AS YEAR, NULL AS MONTH, flag1, flag2, flag3
FROM a_table
GROUP BY flag1, flag2, flag3;

CUBE 的另一个例子：

SELECT COUNT(DISTINCT SID), YEAR, MONTH, flag1, flag2, flag3, GROUPING_ID(flag1, flag2, flag3) AS flag_ID
FROM a_table
GROUP BY YEAR, MONTH, CUBE(flag1, flag2, flag3)

SELECT COUNT(DISTINCT SID), YEAR, MONTH, flag1, flag2, flag3, 0 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH, flag1, flag2, flag3 
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, MONTH, flag1, flag2, NULL AS flag3, 1 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH, flag1, flag2 
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, MONTH, flag1, NULL AS flag2, flag3, 2 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH, flag1, flag3 
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, MONTH, flag1, NULL AS flag2, NULL AS flag3, 3 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH, flag1 
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, MONTH, NULL AS flag1, flag2, flag3, 4 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH, flag2, flag3 
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, MONTH, NULL AS flag1, flag2, NULL AS flag3, 5 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH, flag2 
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, MONTH, NULL AS flag1, NULL AS flag2, flag3, 6 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH, flag3 
UNION ALL
SELECT COUNT(DISTINCT SID), YEAR, MONTH, NULL AS flag1, NULL AS flag2, NULL AS flag3, 7 AS flag_id 
FROM a_table 
GROUP BY YEAR, MONTH

您可以在一个 GROUP BY 子句中同时使用 ROLLUP 和 CUBE。

您可以在此处找到 ROLLUP 和 CUBE 子句文档：http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_10002.htm#SQLRF55331

检查功能还包括GROUPING_ID 和GROUPING。例如，您可以在 HAVING 子句中使用它来根据您的需要限制输出。