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.

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Definition of List, Set, Container, and Map

 

Difference between List, Set, Container, and Map

Containers:

Containers are dynamic and have no limits. They can contain elements of
almost all data types: boolean, integer, real, date, string, container,
arrays, tables, and extended data types. However, objects may not be stored
in containers.

Containers in AX are used very often. It’s easy to work with them. But…
data in containers are stored sequentially and thus retrieved sequentially.
This means that containers provide slower data access if you are working with
_large numbers_ of records. In case of large numbers of records use temporary
tables.

List:

Lists are structures that may contain any number of elements that are
accessed sequentially. Lists may contain values of any X++ type. All the
values in the list must be of __the same__(this is the main difference
between lists and containers) type, given in the creation of the list. The
implementation of lists is such that the traversal of the list elements is __very
fast.

Take a look for example at the class Dialog addControl() method.
Their controls are stored in ctrls List.

Map:

A map is a data type that associates one (key) value with another value [An
analog – a small table in memory with two fields: Keys, Values]. Both the key
and value values may be of any valid X++ type, including objects. The types
of the key and the value are given in the declaration of the map. The
implementation of maps is such that access to the values is _very fast_.

Don’t confuse map X++ types with Map objects in AOT, which are used for
mapping tables with similar structures of fields
–

Set:

The functionality of Sets is similar to the list.  A Set is just an unordered list of items, while a list of items held by a Map
are indexed via a key.
Take look at
\Classes\sysLabel\LabelModuleId().

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