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Siebel Tools Reference > Adding Custom Extensions to the Data Model > Updating the Logical Schema Definition in the Local Environment >

Adding Extension Columns to Tables

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You can add extension columns to any of the following table types:

• Data tables
• Intersection tables
• Interface tables
• Standard extension tables
• Custom extension tables
• Extension (Siebel)

You should check the Type property for a table to verify that you can extend it:

• You cannot add extension columns to private data tables—that is, tables with a Type property of Data (Private).
• Some interface tables are private, although most are public.

NOTE:  For Oracle databases, the maximum length of extension columns with data type of Varchar is 2000 characters. If you create a column of type Varchar that is longer than 2000, it is implemented as a column with data type of LONG.

To add an extension column

1. Connect to your local development database with Siebel Tools.
2. In the Object Explorer, expand the Table object type.
3. In the Object List Editor, select the table to which you will add an extension column or columns.
4. Make sure that the table is not of type Data (Private).
5. Select Column in the Object Explorer.
6. Select Edit > New Record to add an extension column.

   NOTE:  Do not use column names that are reserved words on your server or client database.

When you add columns to base tables or interface tables, Siebel Tools enforces the naming conventions described in the section Naming Conventions for Extension Tables and Columns.

You must provide a default value, in the Default property, for any column that you designate as mandatory (with a FALSE value in the Nullable property). Although you can create a mandatory column without providing a default, you will encounter problems when using this column. For example, if you try to add a column to a table that is already populated with data, the database will fail to create the column. If the table does not yet contain data, attempts to add data (through the user interface, Enterprise Integration Manager, or Siebel Remote) may fail.

In an extension column, use only default values for the following properties:

• Translate
• Use FKey
• Sequence Object
• Cascade Clear
• Foreign Key Table Name

CAUTION:  Be extremely careful when using custom extension columns to track foreign keys. If you choose to implement this, you must consult with Siebel Expert Services concerning the visibility rules applied to the foreign key table. Additionally, you must set the Foreign Key Table Name property to NULL for that column to load values into it using Enterprise Integration Manager.

For information on creating foreign key mappings for EIM, see EIM Table Mapping Wizard.

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