if OBJECT_ID('tempdb..#t') is not null
	drop table #t

Create table #t ([key] int, [type] sysname)

insert into #t
Values 
 (1, 'varchar(10)')
,(1, 'varchar(20)')
,(1, 'varchar(12)')
,(1, 'varchar(9)')
,(2, 'datetime2')
,(2, 'datetime')
,(2, 'date')
,(3, 'numeric(4,2)')
,(3, 'numeric(18,4)')
,(3, 'nimeric(11,5)')

 Select *, SQL_VARIANT_PROPERTY(t.n, 'BaseType'), SQL_VARIANT_PROPERTY(t.n, 'Precision') , SQL_VARIANT_PROPERTY(t.n, 'Scale')
from (
Select try_Cast('' as tinyint)
Union all 
Select try_Cast(Null as smallint)
) t(n)

declare @t table ([key] int, [type] sysname);

insert into @t
Values 
 (1, 'varchar(10)')
,(1, 'varchar(20)')
,(1, 'varchar(12)')
,(1, 'varchar(9)')
,(2, 'datetime2')
,(2, 'datetime')
,(2, 'date')
,(3, 'numeric(4,2)')
,(3, 'numeric(18,4)')
,(3, 'numeric(11,5)');

Select [key], system_type_name from (
Select tt.[key], stuff(q.txt, 1, len('Union All '), '')
from
	(Select distinct t.[key] from @t t) tt
	Cross apply (
	Select 
		'Union All Select cast('''' as ' +  t.[type] + ') '
		from @t t
		where t.[key] = tt.[key] 
		for xml path('')
		) q(txt)
	) a([key], txt)
 cross apply
 sys.dm_exec_describe_first_result_set(a.txt, null, 0) b;