## Creating joins between tables

The Pre-join Editor is a convenient tool for you to predefine the relationships among tables all at once.

To predefine joins among tables in a catalog, follow the steps below:

1. In JReport Designer, open the catalog on which you want to define join relationships.
2. In the Catalog Browser, select a data source to activate the Pre-join button on the toolbar if it is disabled.
3. Click the button, then in the Select Data Source dialog, select the date source on which the joins will be created and click OK. The Pre-join Editor window appears.
4. Click the Arrange button to organize the tables that have been added to the catalog.
5. Now you can make joins among tables by using mouse drag and drop. Point to one column in the source table, press and hold the mouse button, then, move the pointer to the other column in the target table and release the mouse button. A green line with a join button will be shown, linking the two columns. This represents that a join has been created.
6. Repeat the above step to set up more joins.

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