User manual

Chapter 3
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Working with related tables and files 71
For more information about relationships, see Help.
Relational database terminology
Before you begin working with relational databases and lookups, you
should understand the following terms. These terms are explained in
the sections that follow.
Term Description
Current table For relational databases, the table that you are currently
working in.
For lookups, the table that the data is copied to.
External table A table outside of the current file, in another file.
Lookup target field
(for lookups only)
The field in a table that you want data copied to during a
lookup.
Lookup source field
(for lookups only)
The field in the related table that contains the data you
want copied during a lookup.
Match field A field in the current table and a field in a related table that
each contains values used to access matching records. (A
match field is sometimes called a key field.) For each
relationship, you select one or more match fields in each
table.
For relational databases, values in match fields must
match each other in some way for a relationship to be
established between the files. See “About match fields for
relationships” on page 72.
For lookups, values in match fields do not have to be equal
to match.
Portal A layout object that displays records from related tables.
Portals display data from related fields in rows, one record
in each row.
Related field A field in one table that is related to a field in another table
(or to a different field within the same table). If a
relationship has been created between two tables (even
through another table), data in fields in one table can be
accessed from the other table.
Related record A record in the related table whose match field (according
to the relationship used) contains a value that matches the
value in the match field of another table.
Related table For relational databases, the table that contains the data
you want to access and work with in the current table.
For lookups, the table that contains the data to copy.
A table can be related to itself. This is called a self-join.
Relational operators In the relationships graph, the symbols that define the
match criteria between one or more pairs of fields in two
tables. These include: equal (=), not equal (≠), greater than
(>), greater than or equal to (≥), less than (<), less than or
equal to (≤), and all rows, or cartesian product (X).
Relationship Relationships provide access to data from one table to
another. Relationships can join one record in one table to
one record in another table, one record to many other
records, or all records in one table to all records in another
table, depending on the criteria you specify when you
create the relationship in the relationships graph. (A
relationship is sometimes called a link or a join
expression.)
Relationships graph In the Relationships tab of the Define Database dialog
box, you can see the occurrences of tables both in the
current file and from any external, related database files.
In this relationships graph, you join tables and change
relationships between fields in different tables.
When you create a new table, a visual representation, or
occurrence, of the table appears in the relationships graph.
You can specify multiple occurrences (with unique
names) of the same table in order to work with complex
relationships in the graph.
Source file The file from which you add a table to the relationships
graph.
Source table The table upon which one or more tables in the
relationships graph are based. The source table is the table
defined in the Tables tab of the Define Database dialog
box.
Term Description