Table Collapsings

Table collapsing consists in merging tables in order to eliminate joins and to improve query performance. You can collapse tables related to each other with a reference or tables with identical primary keys.

1. Select  Tools  Denormalization  Table Collapsing , or right-click a reference between the tables to collapse and select Table Collapsing to open the Table Collapsing Wizard.
2. Specify a name and code for the table to be created, and then click Next.
3. Click the Add Tables tool to select tables to collapse into the new table, specify whether you want to keep the original tables after collapsing, and then click Next.
4. Specify a name and code for the transformation object that will be created to preserve information about the collapsing, and then click Finish to collapse the selected tables into a single unified table (with graphical synonyms replacing each original table symbol in the diagram to minimize disruption of references.

   In this example, the tables Customer and Order are collapsed together to eliminate the join and optimize data retrieval. The result is a single table (with 2 synonym symbols) with the primary key of the child table:

   Before	After

5. [optional] Delete one of more of the synonyms. References will redirect to the remaining symbol.