Part III: More-Advanced Access Techniques
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Setting view properties
Although an external table is used like another Access table, you can’t change the structure (delete,
add, or rearrange fields) of an external table. You can, however, set several table properties for the
fields in a linked table:l (^) Format
l Decimal places
l (^) Caption
l Input mask
l (^) Unicode compressions
l IME sequence mode
l (^) Display control
Setting relationships
Tip
Access enables you to set permanent relations at the table level between linked non-Access tables and native
Access tables through the Relationships Builder. You can’t, however, set referential integrity between linked
tables, or between linked tables and internal tables. Access enables you to create forms and reports based on
relationships set up in the Relationships Builder, such as building a SQL statement used as the RecordSource
property of a form or report.
Linking to external Access tables maintains the relationships that might exist between the external
tables. Therefore, when linking to a back-end database, the relationships you’ve established in the
back end are recognized and honored by the front-end database. This is a good thing, since it
means that the rules you’ve defined will be enforced regardless of how many front ends are created
to use the tables.
Optimizing linked tables
When working with linked tables, Access has to retrieve records from another file. This process
takes time, especially when the table resides on a network or in an SQL database. When working
with external data, optimize performance by observing these basic rules:
l Avoid using functions in query criteria. This is especially true for aggregate functions,
such as DTotal or DCount, which retrieve all records from the linked table before per-
forming the query operation.
l (^) Limit the number of external records to view. Create a query using criteria that limit
the number of records from an external table. This query can then be used by other que-
ries, forms, or reports.