The query below lists tables in a database without primary keys.
select schema_name(tab.schema_id) as [schema_name], tab.[name] as table_name from sys.tables as tab left outer join sys.indexes as pk on tab.object_id = pk.object_id and pk.is_primary_key = 1 where pk.object_id is null order by schema_name(tab.schema_id), tab.[name]
Below is a list of tables without primary keys.
Is that a lot? Check out here.