Question

Oracle

从table1中选择*;

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      |

是否可以做这样的事情。

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，我在SUM()周围添加了colum3聚合函数，以防每个column1, column2重复值。

根据您使用的数据库，以下等效查询可能会更快一些：

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，您可以使用PIVOT子句以更简洁的方式实现相同的目标（正如其他人所建议的那样）。在 Oracle 11g 中，这将转换为：

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

在任何情况下，我都不知道任何允许每个表表达式动态列数的数据库，而不需要使用涉及XML或其他动态SQL方法的技巧。通常，这些技巧并不比我在这里建议的快得多。这意味着，您将始终需要预见，您希望作为列支持多少年，并相应地调整您的查询

Answer 2

在SQL服务器中尝试PIVOT

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

<强> EDIT1 ：

如果您的Column2是动态的，请尝试以下操作：

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)

SQL。可能吗？

2 个答案: