Tables Overview

Artikel
05/18/2015

Applies To: Microsoft Dynamics AX 2012 R3, Microsoft Dynamics AX 2012 R2, Microsoft Dynamics AX 2012 Feature Pack, Microsoft Dynamics AX 2012

Tables are the foundation objects in Microsoft Dynamics AX and store data used by the system. A table is made up of records (or rows) that contain information about a single entry in the table. For example, a specific customer or product. A record consists of one or more fields (or columns) that contain a discrete piece of data of a specific data type.

In Microsoft Dynamics AX, tables are located in the Application Object Tree (AOT) under the Data Dictionary\Tables node. Each table contains the following primary elements:

Fields
Field Groups
Indexes
Relations
DeleteActions
Methods

A table name can contain letters and numbers but must begin with a letter. Spaces and special characters are not allowed. For more information about adding tables, see How to: Create Tables.

Fields

The Fields node contains all the fields in the table. By specifying a field's data type, you define the type of data that can be stored in it. Microsoft Dynamics AX performs data validation to ensure that only valid data is entered into each field in the table. Constraints are also added to the database to set default field values if a field is left blank.

Each field in a table has a number of properties that describe the behavior of the field. The Type property contains the native data type of the field. The ExtendedDataType property contains the extended data type value (if the field is based on an extended data type). For more information about field properties, see Table Field Properties.

System Fields

When a new table is created, system fields are automatically added to each table. These fields are in the database table but aren't visible in the AOT Fields node. The system fields that are appended to a table depend on the value of particular table properties as shown in the following table.

System field	Table property
RecId	Always
RecVersion	Always
DataAreaId	SaveDataPerCompany = Yes
CreatedBy	CreatedBy = Yes
CreatedDate	CreatedDate = Yes
CreatedTime	CreatedTime = Yes
CreateTransactionId	CreateTransactionId = Yes
ModifiedBy	ModifiedBy = Yes
ModifiedDate	ModifiedDate = Yes
ModifiedTime	ModifiedTime = Yes
ModifiedTransactionId	ModifiedTransactionId = Yes

Field Groups

Field groups are objects that group together fields that logically belong together. For more information about field groups, see Best Practices for Field Groups, Defining Field Groups,and How to: Create a Field Group.

Indexes

An index is a table-specific database structure that speeds the retrieval of rows from the table. Indexes are used to improve the performance of data retrieval and sometimes to ensure the existence of unique records. It's up to the database-specific query optimizer to use available indexes to facilitate efficient data retrieval.

The AllowDuplicates property on the index has the biggest impact on how the index is used. When set to No, the system creates a unique index on the specified fields in the database. Otherwise, a non-unique index is created. For more information about indexes and keys, see Indexes Overview.

System Index

Microsoft Dynamics AX requires a unique index on each table. If there are no indexes on a table or all the indexes are disabled, a system index is automatically created. The system index is created on the RecId and DataAreaId fields if the DataAreaId field exists. Otherwise, the system index is created on the RecId field. You can see system indexes in the database, but they aren't visible in the AOT.

If there are indexes on a table but none of them are unique, the runtime estimates the average key length of the existing indexes, selects the index with the smallest key length, and then appends the RecId column to create a unique index.

Relations

Relations define the relationship between two tables that contain related data. Table relations are used to enforce referential integrity among other functions.

Table relations are most commonly used in form fields to enable the look-up of information in another table. If a table relation exists, the Lookup button can be used to display a lookup list of values for a particular field. For more information about table relations, see Defining Table Relations.

DeleteActions

The DeleteAction element is used to maintain database consistency when a record is deleted. Define delete actions to specify what should occur when data being deleted in the current table is related to data in another table. The delete action values are None, Cascade, Restricted, and Cascade + Restricted. For more information about delete actions, see Maintaining Data Integrity and How to: Create Delete Actions.

Methods

The Methods node displays all the methods available from a table. Use this node to add a new method, or override methods on the Table kernel class and add your own code.

Add a New Method

Browse to the Data Dictionary, Tables node in the AOT.
Expand the table, right-click the Methods node, and then select New Method.
Enter your code in the Editor window and save your changes.

Override a Method

Browse to the Data Dictionary, Tables node in the AOT.
Expand the table, right-click the Methods node, and then select Override Method.
Select the method that you want to override.
Enter your code in the Editor window, and then save your changes.

Methods that have been overridden display an icon with an arrow.

For more information about using methods in your tables, see Table Methods.

Table properties

The table has a number of properties that define its behavior. For more information about customizing your tables, see Table Properties.

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