I have a challenging SQL query to work out (SQL Server). I have one table that will show mappings between the two tables. So below, field F1 is a scanner id

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and table two, has the scanner Id in F1. F2 has the Location, and so on.

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The top table can be updated to change mappings at any time. So my question is how do I create a query so I know what field name relates to what data in table two.

I started off with an UNPIVOT, but didn't get too far as yet. If I could get the field name in the unpivot results then I am a long way to solving it.

ID,[F1] ,[F2]  ,[F3]  ,[F4]  ,[F5]  ,[F6]  ,[F7]  ,[F8]  ,[F9] ,[F10]
FROM [Inventory].[dbo].[ScannedDataCapture]

) AS cp
Data FOR Datas IN ([F1] ,[F2]  ,[F3]  ,[F4]  ,[F5]  ,[F6]  ,[F7]  ,[F8]  ,[F9] ,[F10])
) AS x

Thanks upfront. Scott

  • Did you try using dynamic SQL?
    – BuahahaXD
    Mar 24 '16 at 13:56
  • Its a consideration certainly. I may try also to hit it as the C# end (source input) Cheers Mar 24 '16 at 14:09

You can use FOR XML PATH to help construct a dynamic query:

-- Generate a list of field names to be used in the SELECT statement
    SELECT '[' + FieldNumber + '] AS [' + FieldName + '],'
    FROM Datas
    ORDER BY FieldName DESC -- Sample column ordering
    FOR XML PATH('')

-- Generate a SELECT query; make sure to remove the comma after the last field
SET @Sql = 'SELECT ' + SUBSTRING(@Sql,1, LEN(@Sql) - 1) + ' FROM dbo.ScannedDataCapture'

-- Show SQL before execution
EXEC sp_sqlexec @Sql

Screenshot of dynamic query output

  • that will worked perfect. Thanks for your advice. Scott Mar 27 '16 at 13:34

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