Get started with table extensions

  • 5 minutes

The TableExtension object is used to extend existing tables in the Business Central application. The following key points are important to know about TableExtension objects.

  • With a table extension, you can modify some table properties but not all of them. For example, you can't change the ID and the Name properties.

  • You can add new fields and modify some properties of existing fields, but you can't delete existing fields. If you have a field of type Text or Code, and want to change the length of that field, you can't because that's not possible.

  • You can create new secondary keys but not modify or remove existing keys.

Creating a table extension works the same way as creating a table, by using the ttableext snippet. Additionally, you can add fields like you would add fields to a normal table by using the tfield snippet.

Every table extension has its own name. As previously discussed in the Work with tables in Dynamics 365 Business Central module, we recommend that you use a prefix or suffix in the name of your object so that it's unique. For each field in the table extension, you need to specify a prefix or suffix in the name of the field.

A basic example of a Table Extension in AL.

To modify an existing field in a table, you can use the modify keyword. No snippet exists for modifying a field in a table.

Example of how to create a Table Extension modify field.