The singleton table type contains system or functional application control information, often referred to as setup. There is one setup table per functional application area, for example, one for Sales & Receivables, one for Purchases & Payables, one for General Ledger, and one for Inventory. Setup tables contain only a single record. Since a setup table has only one record, it can have a primary key field that has no value assigned to it (this is how all of the standard Business Central setup tables are designed). The singleton table design pattern can be found at http://blogs.msdn.com/b/nav/archive/2013/07/19/nav-design-pattern-of-the-week-single-record-setup-table.aspx.
The Inventory Setup page is as follows:
