The Join tool provides a graphical method for creating and manipulating Joins. You must specify a host file, then a cross-referenced file to create a join.

You create the Join as an object, separate from any other object or procedure. You are responsible for placing the Join object in the correct position within your procedure (that is, before a Define, Report, or Graph), and for running it. The Join remains active for the entire session, unless you explicitly clear it.

You can open the Join tool from either the toolbar or from a reporting tool. Before the tool opens you will be asked to select a host file.

The Join tool displays both files and, ordinarily, a default Join:

• A Join is represented by a connector line from the host Join field to the cross-referenced Join field. A single arrow indicates a single instance Join; a double arrow indicates a multiple instance Join, the default Join type.
• Developer Studio automatically creates a Join between the files if they both have fields with the same formats (and, for a FOCUS file, if the cross-referenced field is indexed). You can use the Toggle Auto Join feature to perform automatic joins within tables. You can use the default Join as it is, or you can customize the Join. If multiple fields have the appropriate format, the default Join is not created unless one of these fields has the same name as the host field. In this case you must specify a join explicitly.
• A host file is indicated by a yellow caption. A cross-referenced file is indicated by a blue caption.
• Indexed fields have a key icon in front of the field, and virtual fields have a define icon in front of the field. A virtual field is a temporary field that does not actually exist in the data source; its value is computed based on an expression you write. After it is created, the virtual field is treated as if it were a field in the data source.
• By default, the list of field names in each data source displays in the Join window. You can change the display to show the following additional information about each field, if it is available in the Master File: alias, format, title, and description.

Note: The syntax identifies if the join is an inner, left outer, unique, or non-unique join. When you open a join in the Join tool that was created prior to Version 7, Release 1 you need to specify the join type. For details on specifying the join type (join properties), see the documentation related to the Join Properties dialog box.

When you exit the Join window, you are prompted to save your work. If you save the Join, it is added to the procedure in which it has been created.

Note: You may also select Save from the Developer Studio File menu, or select the Save icon from the Join toolbar.

The Join tool preserves the table sizing and positioning when you re-open the tool. The Join tool displays Joins that use some of the same files in one panel of the Join window. The following two Joins share a host file:

Tip: If the field names you wish to join are different, you must drag and drop the field names to make the connection.

Note: If you close the Join window and then reopen it, the two Joins appear in the same panel.

You can customize an existing Join by changing the files or fields involved. If no default Join was created, you can use the same technique to specify a connection explicitly.

You can also change the Join name, make the Join a single instance, use a virtual field as the Join field, and add tag names to the Join files.

A default name is automatically assigned to each Join.

You can use the Join name to later clear the Join and to prevent another Join from overwriting it. If you remove the Join name completely, any subsequent unnamed Join will overwrite this Join.