SQL。可能吗？

Question

Oracle

select * from table1;

column1 |  column2 | column3 | 
a  |  2010  |  1  | 
a  |  2011  |  2  | 
a  |  2012  |  3  | 
b  |  2010  |  4  | 
b  |  2011  |  5  | 
b  |  2012  |  6  | 
c  |  2010  |  7  | 
c  |  2011  |  8  | 
c  |  2012  |  9  | 

是否可以这样做。

column1 | 2010 | 2011 | 2012 | 
a  |  1  |  2  |  3  | 
b  |  4  |  5  |  6  | 
c  |  7  |  8  |  9  | 

Answer 1

是

SELECT t.column1, 
     (SELECT SUM(column3) FROM table1 
     WHERE column1 = t.column1 AND column2 = 2010) AS "2010", 
     (SELECT SUM(column3) FROM table1 
     WHERE column1 = t.column1 AND column2 = 2011) AS "2011", 
     (SELECT SUM(column3) FROM table1 
     WHERE column1 = t.column1 AND column2 = 2012) AS "2012" 
FROM (
    SELECT DISTINCT column1 FROM table1 
) t 
ORDER BY t.column1 

注意，我已经添加了SUM()聚合函数的情况下，各地colum3你可以每column1, column2有重复的值。

，取决于您所使用的数据库，下面的等效查询可能会更快一点：

SELECT t.column1, 
     (SELECT SUM(column3) FROM table1 
     WHERE column1 = t.column1 AND column2 = 2010) AS "2010", 
     (SELECT SUM(column3) FROM table1 
     WHERE column1 = t.column1 AND column2 = 2011) AS "2011", 
     (SELECT SUM(column3) FROM table1 
     WHERE column1 = t.column1 AND column2 = 2012) AS "2012" 
FROM table1 t 
GROUP BY t.column1 
ORDER BY t.column1 

请注意，您也可以达到同样以更简洁的方式，使用PIVOT条款（如其他已建议）。在的Oracle 11g，这将转化：

SELECT column1, "2010", "2011", "2012" 
FROM table1 
PIVOT (SUM(column3) FOR column2 IN (2010, 2011, 2012)) 

在任何情况下，我不知道，允许每个表表达式列的动态数量的任何数据库，而不诉诸涉及XML或其它手段花样的动态SQL。通常，这些技巧并不比我在这里提出的要快得多。这意味着，你总能预见到，你要多少年，以支持为列，并适应您的查询相应

Answer 2

尝试PIVOT在SQL断绝

select column1 , [2010],[2011],[2012] 
from your_table 
PIVOT (MAX(column3) FOR column2 IN ([2010],[2011],[2012])) P 

EDIT1：

如果Column2是动态的，那么试试这个：

DECLARE @cols AS NVARCHAR(MAX), 
    @query AS NVARCHAR(MAX) 

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(column2) 
        from your_table 
      FOR XML PATH(''), TYPE 
      ).value('.', 'NVARCHAR(MAX)') 
     ,1,1,'') 



set @query = 'SELECT column1 , ' + @cols + ' from your_table 
      pivot 
      (
       MAX(column3) 
       for column2 in (' + @cols + ') 
      ) p ' 
print(@query) 
execute(@query)