User manual

Working with related tables and files 63
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 64.
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