Define Join Relationships

Joins are defined by specifying the fields that link a record in one object to a record in another object.

About Joins

A "join" is a concatenation of fields from two objects that have the same data for a field they have in common (even though the fields generally have different names). So if object A has records with values 1, 2, 3, 4 in field "x", and object "B" has values 3, 4, 5, 6 in field "y", then the different kinds of "joins" produce rows like the following:

Row	Record data from "A"	Record data from "B"	Type of Join
1 2	x=1,... x=2,...	none none	Non-matching rows, returned only in a "left join".
3 4	x=3,... x=4,...	y=3,... y=4,...	Matching rows returned in a "left join" or "right join". The only rows returned by an "equi-join" (typically the default).
5 6	none none	y=5,... y=6,...	Non-matching rows, returned only in a "right join".

Important: Joining fields should be indexed, for performance. In the example above, field "x" should be indexed in A, and field "y" should be indexed in B.

Join Theory

In a join, choose at least one object that contains an ownership record. The reason:

• The Filter by Record Ownership option is commonly used for Reports based on Database Views.

About creating joins:

• When two objects are selected, a single, mandatory relationship (Join) must be specified
• When three objects are selected (e.g. A, B and C), two mandatory relationships must be specified
• The drop down lists fields that available for use in a Join.
  In general, the following kinds of fields can be used:
  • Record ID fields (fields containing a record identifier)
  • Lookup fields
  • Fields that contain raw data values like number or string.

Note: One common convention for numeric identifier fields is to end them with '#'. That convention can make it easier to identify fields that can be used for a join. For example: SocialSecurity# or Account#.

Rules for Joins

When creating joins, note that each join is dependent on the previously defined join.

For example, consider the case where we have three tables: A, B and C. In these joins, the first join row defines the possibilities for the second row:

A.id <join type> B.id
A.id <join type> C.id

or

A.id <join type> B.id
B.id <join type> C.id

where <join type> is Left, Right or Equi

Example Join

In this example, we have a two objects: instruments and players in a band. As you might expect, the players in the band might play multiple instruments, and multiple instruments may be available to the band members. As is true with many bands, this band needs a drummer, and some players do vocals only.

Object A		Object B
instrument_ID	Instrument	player_ID	Players	Can Play Instrument
IN1	Guitar	P1	Bill Bertie	IN1
IN2	Keyboard	P1	Bill Bertie	IN4
IN3	Drums	P2	Madeline Morris	IN2
IN4	Accordion	P2	Madeline Morris	IN4
		P3	Sissy Smith	IN2
		P3	Sissy Smith	IN4
		P4	Kerry Kline	IN1
		P5	Crissy Clemens
		P6	Gary Green

Using Joins

Joins are a means to relate two objects (tabs) in order to build reports containing fields from both objects. There are three types of joins:

• Left-Join
• Right-Join
• Equi-Join

Left-Join

When objects A and B are related with a Left-Join, the report includes all records in object A, and all matching records in object B. Using the example above, the resulting report would include these records:

Left-Join Report
instrument_ID	Instrument	Played by
IN1	Guitar	Bill Bertie Kerry Kline
IN2	Keyboard	Madeline Morris Sissy Smith
IN3	Drums
IN4	Accordion	Madeline Morris Sissy Smith

Right-Join

When objects A and B are related with a Right-Join, the report includes all records in object B, and all matching records in object A. Using the example above, the resulting report would include these records:

Right-Join Report
instrument_ID	Instrument	Played by
IN1	Guitar	Bill Bertie Kerry Kline
IN2	Keyboard	Madeline Morris Sissy Smith
IN4	Accordion	Madeline Morris Sissy Smith
		Crissy Clemens
		Gary Green

Equi-Join

When objects A and B are related with an Equi-Join, the report includes all records where a record in object B is related to a record in object A. Using the example above, the resulting report would include these records:

Equi-Join Report
instrument_ID	Instrument	Played by
IN1	Guitar	Bill Bertie Kerry Kline
IN2	Keyboard	Madeline Morris Sissy Smith
IN4	Accordion	Madeline Morris Sissy Smith