DROP PROCEDURE IF EXISTS dev.uspDropDefaultConstraint
GO

CREATE PROCEDURE dev.uspDropDefaultConstraint
   @pTableName nvarchar(80)
  ,@pColumnName nvarchar(80)
AS
BEGIN
  DECLARE @sql nvarchar(max)

  SELECT 
    @sql = 'ALTER TABLE ' + @pTableName + ' DROP CONSTRAINT ' + df.name 
  FROM sys.default_constraints df
    INNER JOIN sys.columns cn ON cn.default_object_id = df.object_id
    INNER JOIN sys.tables tb ON tb.object_id = cn.object_id
  WHERE cn.name =  @pColumnName
    AND tb.name = @pTableName

  EXEC sp_executesql @sql
END
GO