Difference Between Replacement key, Alternate key, Surrogate key in AX 2012 and D365FO

 


  Replacement key, Alternate key, and Surrogate key


WHAT IS A REPLACEMENT KEY INDEX?
While a surrogate key is great for lookup and database performance, it is not useful for the end-user because it gives no indication of the table’s purpose, or what related tables it is linked to. For this reason,  Dynamics 365 Finance & Operations has added the ‘Replacement Key’ index property for tables. The replacement key index is a dropdown of alternate keys that have been specified for the table. There can be any number of alternate keys for a table but only a single replacement key. More than one field can be specified under a replacement key, and it is these fields that will be displayed to the end-user on a form instead of the surrogate key field.

A replacement key is an alternate key that the system can display on forms instead of a meaningless numeric primary key value. Each table can have a maximum of one replacement key.


The replacement key is chosen by setting the ReplacementKey property on the table. The drop-down list offers every alternate key as an available value.

WHAT IS AN ALTERNATE KEY?
A table can have any number of alternate keys. An alternate key may be a natural key or a single field primary key used in foreign or primary key relations with other tables. In either case, to set one, the user must create a new index and then set AllowDuplicates to “No” and AlternateKey to “Yes”. If AllowDuplicates is not set to “No” then AlternateKey should be greyed out and uneditable

WHAT IS A SURROGATE KEY?

In Dynamics 365 Finance & Operations, a surrogate key is the auto-generated primary key for a table in the database. The surrogate key is linked to the already existing RecId field within any table. This means that the surrogate key is a unique 64-bit integer value that is mandatory for the table and cannot be changed or have duplicates. The fact that it is a 64-bit integer (int64) value means table operations normally perform faster than other types of fields such as string fields. This is the main strength of surrogate keys.