使用字符串列旋转 SQL 表的语法错误

Posted 2023-05-08

【中文标题】使用字符串列旋转 SQL 表的语法错误

【英文标题】：Syntax Error pivoting a SQL table using string columns

【发布时间】：2020-12-09 20:01:52

【问题描述】：

我有一张职业这样的桌子：

Name | Occupation
-----------------
Sam  | Doctor
Joe  | Professor
John | Actor
Hailey | Singer
April | Doctor

我的目标是利用 PIVOT 函数将每个不同的职业显示为自己的列，如下所示：

Doctor | Professor | Singer | Actor
-----------------------------------
Sam    | Joe       | Hailey  | John
April

我经历了各种类似问题的堆栈溢出问题，甚至利用了这里的文档并一步一步地跟进。我的努力是徒劳的，那又是什么呢？每次运行此代码时，我都会收到语法错误。有什么建议吗？

代码：

SELECT *
FROM(SELECT Name, Occupation from Occupations) as src
PIVOT
(MAX(Name) FOR Name IN [Doctor], [Professor], [Singer], [Actor]) as piv;

我在 Hackerrank 上解决这个问题，编译器是 mysql。我将其更改为 MSSQL，并且不再收到语法错误。

【参考方案1】：

您在 PIVOT 部分的每一侧都缺少 2 () 一个，我将添加的括号加粗：

([医生]、[教授]、[歌手]、[演员])——这2个

SELECT *
FROM (
    SELECT Name, Occupation 
    FROM Occupations
) as src
PIVOT
(
    MAX(Name) FOR Name IN ([Doctor], [Professor], [Singer], [Actor])
) as piv;

【讨论】：

我注意到这个愚蠢的错误，我的错。虽然，我在修复它时仍然收到语法错误。

【参考方案2】：

此查询将根据您的需要生成答案。上述答案并未按照您的要求提供答案。试试这个答案。

DECLARE @sql NVARCHAR(MAX) = N''
DECLARE @cols NVARCHAR(MAX) = N''

--Making the column list dynamically 
SELECT @cols  = STUFF((SELECT DISTINCT ', '+QUOTENAME(  [T2].[Occupation]) 
               FROM  Occupation_data [T2]              
               FOR XML PATH('')), 1, 1, '')              


 --preparing PIVOT query dynamically. 

 SET @SQL = ' SELECT 

            *
          into #temp
          FROM 
          (
          SELECT row_number() over (order by name) as id,  [Name], [Occupation]
          FROM Occupation_data
          ) AS cp
          PIVOT
          (
           min([Name]) FOR [Occupation] IN (' + @cols + ')
          ) AS up;  
             
                
          Select               
          row_number() over (order by doctor asc ) as id1
          ,*
          into  #temp_1
          from #temp where Doctor is not null
         
                     
          Select 
          row_number() over (Order by Actor asc ) as id2
          ,*
          into #temp_2
          from #temp where Actor is not null
                  
         
          Select 
          row_number() over (Order by Professor asc ) as id3
          ,*
          into #temp_3
          from #temp where Professor is not null
        
          Select 
          row_number() over (Order by Singer asc ) as id4
          ,*
          into #temp_4
          from #temp where Singer is not null


          select 
          A.Doctor
          ,B.Actor
          ,C.Professor
          ,D.Singer
          from 
          #temp_1 A inner join 
          #temp_2 B ON A.id1 = B.id2 
          INNER JOIN
          #temp_3  C ON A.id1 = C.id3
          INNER JOIN  
          #temp_4 D ON A.id1 = d.id4
        

          drop table #temp 
          drop table #temp_1
          drop table #temp_2
          drop table #temp_3
          drop table #temp_4

  ';

  PRINT( @SQL)
  EXEC (@SQL)

输出：

如果这个答案对你有用，我会让它更通用并给你，这样你就可以将它应用于任何类似的工作。

【讨论】：

@nick_rinaldi 检查这个答案，让我知道。