A processor is operated to combine a first row of a dimension table in a data warehouse with a second row in the dimension table. The result is a combined row that includes a row identification key for the first row and a row identification key for the second row. The row identification key for the first row joins the combined row to fact data from a prior time period. The second row corresponds to a current time period that is later than the prior time period. The processor is also operated to join at least a portion of the combined row to at least a portion of the corresponding row in a fact table associated with the dimension table. The fact data from the prior time period is included in the corresponding row in the fact table.