Find default constraint names for tables (Sql Server)

find-default-constraint-names.sql

/*
Sql server will not let you dropa table if it has default contraints (like default values for columns.)
This script will let you find them.

1. Determine the constraint name.
*/
if object_id('[dbo].[GetDefaultConstraintName]') is not null
    drop function [dbo].[GetDefaultConstraintName]
go

create function [dbo].[GetDefaultConstraintName] (
    @TableName varchar(max),
    @ColumnName varchar(max))
returns varchar(max)
as
begin

    -- Returns the name of the default constraint for a column

    declare @Command varchar(max)
    select 
        @Command = d.name
    from 
        ((
        sys.tables t join
        sys.default_constraints d
            on 
                d.parent_object_id = t.object_id) join
        sys.columns c
            on 
                c.object_id = t.object_id and 
                c.column_id = d.parent_column_id)
    where 
        t.name = @TableName and 
        c.name = @ColumnName
    return @Command
end
go

/*
2. Generate dynamic sql to drop the constraint. Assume that the table name is MyTable and the column name is MyColumn.
*/
execute ('alter table MyTable drop constraint '+
           [dbo].[GetDefaultConstraintName]('MyTable','MyColumn'))

/*                  
3. Re-create the constraint with the desired default value. Assume that the new default value should be 33.
*/
alter table MyTable add constraint [DF_MyTable_MyColumn] default (33) for MyColumn