Creating Columns 
Prerequisites
You are logged on to the database as a database user.
You are the owner of the table or have the ALTER privilege for the table in which you want to create the column.
More information: SQL Reference Manual, Privilege Specification (priv_spec)
The database is in the ONLINE operational state.
Procedure
In the context menu of the table, choose Definition.
In the context menu of the editor window, choose Edit.
Open the Columns tab page.
In the context menu of the editor window, choose Add Column.
Define the column properties.
Columns Property
Description (Links to SQL Reference Manual)
Name
Data Type
Dim
Dimension
Maximum number of characters
Code Attribute
Key
If you select this option, you add this column to the primary key.
Key Definition (key_definition)
All columns in the primary key must be NOT NULL columns.
You cannot use any columns of the LOB data type in the primary key.
The database ensures that no NULL value exists in the key column and that no two data records in the table have the same values in all key columns.
Not Null
If you select this option, the value for this column cannot be a NULL value.
In the context menu of the editor window, choose Create Table (if you are creating a new table) or Alter Table (if the table already exists).