The [[Invantive Studio/Repository/Concepts/Natural Key|natural key]] of a table is a unique index named after the table alias followed by `_nk`. It is defined as follows: - Open the table in the tree and select its folder "Indexes". - Choose [[Invantive Studio/Ribbon/Add|"Add"]] and name the index `<prefix>_<alias>_nk`, such as `sales_ord_nk`; switch "Unique" on. - Choose [[Invantive Studio/Ribbon/Save|"Save"]]. - Open the new index and select its folder "Columns". - Add each column of the natural key with [[Invantive Studio/Ribbon/Add|"Add"]], giving its "Position" in the index, and choose [[Invantive Studio/Ribbon/Save|"Save"]].