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Linking in VDM (or any query and reporting tool) is required when requesting data from two or more tables. Linking tells VDM how to join the tables together in order to return the requested data set.
In the examples below we are pulling data from the Customers table and the Orders table. Linking tells VDM that the unique data field in Customers is also unique in Orders. The data for the two tables are joined by the CustomerID field. Linking can be a bit challenging in the beginning, but as you become more comfortable with your data and VDM it will become second nature.
To add a new linking select the field from one table/file, displayed within its own box, and drag it the corresponding field in the table/file that you wish to link. VDM will ask what type of join you would like to do; Equal (=) – Implicit, Equal (JOIN) –Explicit, Left, or Right. If you have more than two tables, repeat the task for each table.
For an in depth explanation of Joins, check out our article.
Upon the creation of a new link, VDM will remember the newly created link for future use. The next time the same tables are selected for a View, VDM will automatically create the linking for you.
For an in depth explanation of Linking, check out our video here.