How to detect and remove a column that contains only null values?

Question

In my table table1 there are 6 columns Locations,a,b,c,d,e.

Locations [a]   [b]   [c]  [d]   [e]

[1]       10.00 Null  Null 20.00 Null

[2]         


        

Answer 1

Try this stored procedure with your table name as input.

alter proc USP_DropEmptyColumns 

@TableName varchar(255)
as
begin

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 = @TableName

OPEN getinfo

FETCH NEXT FROM getinfo into @col

WHILE @@FETCH_STATUS = 0
BEGIN
    SELECT @cmd = 'IF NOT EXISTS (SELECT top 1 * FROM [' + @TableName + '] WHERE [' + @col + '] IS NOT NULL) 

                        BEGIN 
                        ALTER TABLE [' + @TableName + ']  DROP Column [' + @col + ']
                        end'
    EXEC(@cmd)

    FETCH NEXT FROM getinfo into @col
END

CLOSE getinfo
DEALLOCATE getinfo

end