Configuring Siebel eBusiness Applications > Configuring Tables and Columns >

Adding Extension Columns to Base Tables

You can add extension columns to existing base tables. Adding an extension column avoids additional joins to extension tables for storing custom attributes. 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 cannot add columns to tables in the following cases:

• 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.

When adding columns to tables, consider the following:

• Review Guidelines for Extending the Data Model.
• Any columns you add must conform to the data type limitations of all the DBMS types used in your Siebel enterprise. Consider your server database as well as any regional or mobile databases.
• 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 automatically implemented as a column with data type of LONG.
• If you add new mandatory columns to an existing table with one or more rows of data, the DBMS will not allow the column to be added unless a default value is provided.
• After a column has been added to the physical table, a column cannot be removed. Refer to your database system's documentation for information on this constraint.
• When you create a new extension column in the Siebel schema, there might be padding issues with Siebel Remote. For more information about Siebel Remote, see Siebel Remote and Replication Manager Administration Guide.
• When you add columns to tables, do not use column names that are reserved words on your server or client database. However, you can use reserved words if you include an underscore ("_") somewhere in the column name. For more information about naming conventions, see About Tables.

CAUTION:  Be extremely careful when using custom extension columns to track foreign keys. If you choose to implement this, it is recommended that you consult with Siebel Systems 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 About Interface Tables.

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.

   The logical database schema is changed based on the information you entered, but you still need to physically apply the changes to your local database as described in Select Edit > New Record to specify each column to add to the index..