/*
  1. change database name.
  2. By default this code prints queries but if you want drop all default values 
     then remove comment from EXEC command.
*/
USE MyBugtrackerDB

DECLARE @TABLE_NAME VARCHAR(128)
DECLARE @COLUMN_NAME VARCHAR(128)
DECLARE @DEFAULT_NAME VARCHAR(128)
DECLARE @CMD VARCHAR(1000)

DECLARE TablesCursor SCROLL CURSOR FOR
	SELECT name AS table_name FROM sysobjects 
	WHERE xtype = 'U' AND Left(name, 7) = 'mantis_'
OPEN TablesCursor
FETCH NEXT FROM TablesCursor INTO @TABLE_NAME 
WHILE @@FETCH_STATUS = 0
BEGIN

	DECLARE ColumnsCursor SCROLL CURSOR FOR
		SELECT so.name FROM sysobjects so 
		INNER JOIN sysconstraints sc ON so.id = sc.constid
		WHERE object_name(so.parent_obj) = @TABLE_NAME
		AND so.xtype = 'D'
	OPEN ColumnsCursor 
	FETCH NEXT FROM ColumnsCursor INTO @DEFAULT_NAME
	WHILE @@FETCH_STATUS = 0
	BEGIN
		SET @CMD = 'ALTER TABLE ' + @TABLE_NAME + ' DROP CONSTRAINT ' + @DEFAULT_NAME
		PRINT @CMD
		--EXEC (@CMD)

		FETCH NEXT FROM ColumnsCursor INTO @DEFAULT_NAME
	END
	CLOSE ColumnsCursor
	DEALLOCATE ColumnsCursor

	FETCH NEXT FROM TablesCursor INTO @TABLE_NAME 
END
CLOSE TablesCursor
DEALLOCATE TablesCursor