Scott Simontis Scott Simontis - 2 months ago 9
SQL Question

Specifying Column Name As A Parameter in SELECT statement?

I need to do something like this, but it always fails with 'Error converting data type varchar to int':

DECLARE @intParam INT
DECLARE @ColName VARCHAR(64)

SET @ColName='intcolumn'

SET @intParam = SELECT @ColName FROM myTable


How do I accomplish something like this? I can see the problem is that the SELECT statement simply returns the column name as a string, but I am not sure how to fix that. I am using SQL Server 2008R2.

Answer

You need to use dynamic sql:

  • build your dynamic SQL query (take a look at @SQL variable in sample below)
  • use output parameter to get value back from dynamic sql (take a look at @intParam and @intParam_out in sample below)
  • execute dynamic sql using sp_executesql
DECLARE @intParam INT
DECLARE @ColName VARCHAR(64)

SET @ColName='intcolumn'

DECLARE @SQL NVARCHAR(1000)
SET @SQL = 'SELECT @intParam_out = ' + @ColName + ' FROM myTable'
exec sp_executesql @SQL, N'@intParam_out int OUTPUT', @intParam_out = @intParam OUTPUT
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