使用动态查询反透视

Question

我正在编写一个查询，根据需要根据表的第一列和选定的行来取消透视表。我在动态查询中遇到了一个问题。实际表有 77 个不同数据类型的列，我试图将其转换为varchar，并且这些值将始终属于表的特定行。 示例：

CREATE TABLE EXAMPLE (ROWDATA INT, CHARDATA VARCHAR(MAX), BIGINTCOLUMN BIGINT)
INSERT INTO EXAMPLE (ROWDATA INT, CHARDATA VARCHAR(MAX), BIGINTCOLUMN BIGINT)
VALUES (1, AB, 15698), (2, BD, 23467), (3, ABC, 42378)

• 现在我想在不放置列的情况下进行反透视操作，以便我可以将其用于多种用途，并且应该只有 2 列，一列是包含值的 ColumnName
• “CHARDATA,BIGINTCOLUMN”其他 ColumnValue 包含诸如“BD,23467”或“ABC,42378”之类的值'

代码：

create table #ColumnName (Countno int identity(1,1), Column_Name varchar(max))
insert into #ColumnName (Column_Name) select COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'EXAMPLE'
Create table #Converttype (Countno int identity(1,1), Converttype varchar(max)) 
insert into #Converttype (Converttype) select case when DATA_TYPE <> 'varchar' then 'Cast(' + COLUMN_NAME + ' as varchar) as '+ COLUMN_NAME else COLUMN_NAME end from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'EXAMPLE'

declare @CreateTable varchar(max) =(select Column_Name from #ColumnName where Countno = 1)
declare @Converttype varchar(max) = (select Converttype from #Converttype where Countno = 1)    
declare @ColumnName varchar(max) = (select Column_Name from #ColumnName where Countno = 2)
declare @Iteration int = (select Count(COLUMN_NAME) from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'EXAMPLE')
declare @count int = 2

while @Count <= @Iteration
begin
    --print @Count

    set @CreateTable = @CreateTable+' varchar(max)' + ',' + (select Column_Name from #ColumnName where Countno = @count) 
    set @Converttype = @Converttype + ',' + (select Converttype from #Converttype where Countno = @count)

    set @count = @count + 1
    set @ColumnName = @ColumnName + ',' + isnull((select Column_Name from #ColumnName where Countno = @count),'') 
end

declare @Unpivot nvarchar(max) = ' 
create table #temp (' + @CreateTable + ' varchar(max))
insert into #temp (ROWDATA,' + @ColumnName + ')
select ' + @Converttype + '  from EXAMPLE where ROWDATA = 2
select * from #temp
unpivot
(
    ColumnValue
    for ColumnName in (' + @ColumnName + ')
) AS Tablecheck'

Exec(@Unpivot)

• 调试后我发现@Unpivot 在我使用 print @Unpivot 时没有特别工作，它没有显示从select * from #temp 到) as Tablecheck 的消息

Answer 1

@ColumnName 末尾的多余逗号只是一个小问题，否则您的脚本可以正常工作。

CREATE TABLE #ColumnName
(Countno     INT IDENTITY(1, 1), 
 Column_Name VARCHAR(MAX)
);
INSERT INTO #ColumnName(Column_Name)
       SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'EXAMPLE';

CREATE TABLE #Converttype
(Countno     INT IDENTITY(1, 1), 
 Converttype VARCHAR(MAX)
); 
INSERT INTO #Converttype(Converttype)
       SELECT CASE
                  WHEN DATA_TYPE <> 'varchar'
                  THEN 'Cast(' + COLUMN_NAME + ' as varchar (max)) as ' + COLUMN_NAME
                  ELSE COLUMN_NAME
              END
       FROM INFORMATION_SCHEMA.COLUMNS
       WHERE TABLE_NAME = 'EXAMPLE';



DECLARE @CreateTable VARCHAR(MAX)=
(
    SELECT Column_Name FROM #ColumnName WHERE Countno = 1
);
DECLARE @Converttype VARCHAR(MAX)=
(
    SELECT Converttype FROM #Converttype WHERE Countno = 1
);
DECLARE @ColumnName VARCHAR(MAX)=
(
    SELECT Column_Name FROM #ColumnName WHERE Countno = 2
);
DECLARE @Iteration INT=
(
    SELECT COUNT(COLUMN_NAME) FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'EXAMPLE'
);

SELECT @Iteration

DECLARE @count INT= 2;
WHILE @Count <= @Iteration
    BEGIN
        print @Count

        SET @CreateTable = @CreateTable + ' varchar(max)' + ',' +
        (
            SELECT Column_Name FROM #ColumnName WHERE Countno = @count
        );
        SET @Converttype = @Converttype + ',' +
        (
            SELECT Converttype FROM #Converttype WHERE Countno = @count
        );
        SET @count = @count + 1;
        SET @ColumnName = @ColumnName + ',' + ISNULL(
        (
            SELECT Column_Name FROM #ColumnName WHERE Countno = @count
        ), '');
    END;



DECLARE @Unpivot NVARCHAR(MAX)= ' 
create table #temp (' + @CreateTable + ' varchar(max))
insert into #temp (ROWDATA,' + SUBSTRING(@ColumnName, 1, LEN(@COLUMNNAME) - 1) + ')
select ' + @Converttype + '  from EXAMPLE where ROWDATA >= 2
select * from #temp
unpivot
(
    ColumnValue
    for ColumnName in (' + SUBSTRING(@ColumnName, 1, LEN(@COLUMNNAME) - 1) + ')
) AS Tablecheck';

print (@unpivot)
EXEC (@Unpivot);

请看 dbfiddle here。