Once you have generated your initial query code, you can select one or more columns to process in your query. You can add columns to your query by checking the box that appears next to a column name in the tree view. Selected columns appear in the tree view with a check mark next to
the column icon,
. Each column name is prefixed by its alias (for example, A.CustID, A.Company). This enables you to distinguish the columns in one table from those in another.