A shortcut join is a join that provides an alternative path between two tables. shortcut joins improve the performance of a query by not taking into account intermediate tables, and so shortening a normally longer join path.
A common use of shortcut joins is to link a shared lookup table to another table further along a join path. The join path comprises several different tables in the same context. In such a case, the shortcut join is only effective when the value being looked up has been denormalized to lower levels in a hierarchy of tables, so the same value exists at all the levels being joined.
In the following example the column Article_code appears in both the tables Product_Promotion_Facts and Shop_Facts. The value of Article_code is the same for both tables. The normal path for a query using Article_code from Product_Promotion_Facts and Shop_Facts, is to pass through the intermediary table Article_Lookup.
The shortcut join directly linking Product_Promotion_Facts and Shop_Facts allows the query to ignore the intermediary table Article_Lookup, optimizing the query.
Designer
does not consider shortcut joins during automatic loop and context detection.
However, if you set the cardinality for a shortcut join you avoid receiving
the message 'Not all cardinalities are set' when detecting contexts.