Once all the dimensional joins have been defined we will be asked to define the unique business key for the staging table. This is the column or columns that allow us to uniquely identify each record in the staging table. In the example below and in our tutorial the unique business key is a combination of the order_number and the order_line_no.

None of the columns chosen as the business key should ever contain a NULL value. See the note at the start of the Dimension chapter.

The 'Include update statement' check box provides two options in the generated procedure. If checked then an update/insert combination will be included. If clear then only an Insert statement will be included in the procedure. If cleared you must be sure that the business key for the table is unique, otherwise either a duplicate key error will occur or records will be lost depending on the type of procedure.