类型和 UDT 不会出现在 sys.objects 中.您应该能够通过以下方式获得所需内容:

select * from sys.types其中 is_user_defined = 1

I need to enumerate all the user defined types created in a SQL Server database with CREATE TYPE, and/or find out whether they have already been defined.

With tables or stored procedures I'd do something like this:

if exists (select * from dbo.sysobjects where name='foobar' and xtype='U')
    drop table foobar

However I can't find the equivalent (or a suitable alternative) for user defined types! I definitely can't see them anywhere in sysobjects.

Can anyone enlighten me?

Types and UDTs don't appear in sys.objects. You should be able to get what you're looking for with the following:

select * from sys.types
where is_user_defined = 1