How to check if the Default Value Constraint exists?

if not exists(select 1 from sys.default_constraints where name = 'SchemaName.MyConstraint')
begin
  -- create it here
end

I find this to be easier:

IF OBJECT_ID('SchemaName.MyConstraint', 'D') IS NULL
BEGIN
    -- create it here
END

I was a bit puzzled as to why this simple task was so complicated. In my case, I don't have constraint names - only table and column names. I want to check if they already have a default before trying to add one.

After a bit more digging, I came up with this:

IF (SELECT Column_Default FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'MY_TABLE' AND COLUMN_NAME = 'MY_COLUMN') is NULL
BEGIN
    ALTER TABLE [dbo].[MY_TABLE]
    ADD DEFAULT ('') FOR [MY_COLUMN]
END
GO

I have to implement this in a ginormous boilerplate script, so the shorter the better.

if not exists (
    select *
      from sys.all_columns c
      join sys.tables t on t.object_id = c.object_id
      join sys.schemas s on s.schema_id = t.schema_id
      join sys.default_constraints d on c.default_object_id = d.object_id
    where t.name = 'table'
      and c.name = 'column'
      and s.name = 'schema')
  ....