编写SQL查询，使用过滤器将一列分成两列

Question

我不是数据库管理员，现在我遇到查询单表的问题。

我得到了如下表格

更新

我想进行查询，如下图所示

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我该怎么办？非常感谢查询谢谢。

Answer 1

你可以这样做：

SELECT MAX(T1.CloseDate) as [Date],
       T1.Job,
       MAX(CASE WHEN T1.WorkRole = 'Case' THEN COALESCE(T2.WorkType,T1.WorkType) END) AS [Case],
       MAX(CASE WHEN T1.WorkRole = 'Engineer' THEN COALESCE(T1.WorkType,T2.WorkType) END) AS [WT]
FROM TableName T1 LEFT JOIN
     TableName T2 ON T1.CloseDate<T2.CloseDate AND T1.Job=T2.Job 
GROUP BY T1.Job
ORDER BY [Date] DESC

结果：

Date                        Job     Case    WT
------------------------------------------------------
January, 01 2008 00:00:00   Senior  Normal  Electronic
January, 01 2005 00:00:00   Junior  Average Electronic

SQL Fiddle中的示例结果。

Answer 2

这称为pivoting。一种方法：

select  CloseDate as [Date]
,       Job
,       max(case WorkRole when 'Case' then WorkType end) as [Case]
,       max(case WorkRole when 'Engineer' then WorkType end) as WT
from    YourTable
group by
        CloseDate
,       Job