Question

How do I select all the columns in a table that only contain NULL values for all the rows? I’m using MS SQL Server 2005. I’m trying to find out which columns are not used in the table so I can delete them.

Answer 1

Here is the sql 2005 or later version: Replace ADDR_Address with your tablename.

declare @col varchar(255), @cmd varchar(max)  DECLARE getinfo cursor for SELECT c.name FROM sys.tables t JOIN sys.columns c ON t.Object_ID = c.Object_ID WHERE t.Name = 'ADDR_Address'  OPEN getinfo  FETCH NEXT FROM getinfo into @col  WHILE @@FETCH_STATUS = 0 BEGIN     SELECT @cmd = 'IF NOT EXISTS (SELECT top 1 * FROM ADDR_Address WHERE [' + @col + '] IS NOT NULL) BEGIN print ''' + @col + ''' end'     EXEC(@cmd)      FETCH NEXT FROM getinfo into @col END  CLOSE getinfo DEALLOCATE getinfo