When you add a field, you must select its data type (see Adding fields to a record type. The data type you select determines
the type of values that the user can enter in the field.
Keep these factors in mind when selecting field types:
- Think through your selections and test them, because it might be difficult
to make changes later.
For example, you cannot modify the field Type or
DB Column Name after you check in the schema; you cannot modify the Maximum
Length property of fields whose type is SHORT_STRING. To make these changes,
you must delete the field and create a new field with similar properties.
- For fields whose data type is SHORT_STRING, enter a value for Maximum
Length that is greater than the longest string that you expect to have. The
effect of a larger value is to reserve more space on the disk drive, which
reduces need to truncate entries.
- A single-string field (MULTILINE_STRING and SHORT_STRING) is suitable
for general information, such as descriptions, comments, and known workarounds.
If you expect to use information in the field for sorting or filtering in
a query, use several smaller fields. For example, instead of one computing
environment field, you might want separate fields for hardware vendor, operating
system, and operating-system version.
- Use several smaller fields if you want to enforce content rules, for example,
requiring telephone numbers to be all digits.
- The SHORT_STRING type is appropriate for fields that contain one selection
from a list of choices (choice list).
The choice list can either be incorporated
into the schema (as a constant list) or maintained through the client interface
(as a dynamic list). The latter method does not require that you change the
schema and upgrade the user database just to add or remove any items on the
list. You can prevent others from adding entries that are not valid by selecting
the Limit to list check box on the choice list property
sheet.
- If you want to provide a set of choices, but let users select more than
one item, you can either provide different fields (and corresponding check
box controls), or you can use a MULTILINE_STRING field and a list box control.
- When testing changes made using a test database, after values are entered
in a field, changing the data type of that field after you click introduces
the risk of data corruption if any values of the old data type are stored
in that field. To alter the field data type after running , delete the field and create
a field with the desired properties and a different data type.
These data types are supported:
- Data
- Description/comments
- ATTACHMENT_LIST
- Allows records to store files related to the record.
- DATE_TIME
- SQL date and time. For more information, see Dates and times.
- INT
- SQL integer.
- MULTILINE_STRING
- A variable-length string of unlimited size.
- REFERENCE
- A reference to a unique key in a record type. For REFERENCE type fields,
you must select a state-based or stateless record type to refer to. You can
also enter an optional back-reference field to create a link from the referenced
record to this field record and can specify that the referenced record type
is under security control.
- REFERENCE_LIST
- Multiple references to unique keys in record types. Reference-list fields
allow you to reference multiple records within a field. You can use reference-list
fields with a parent/child control to link related records. For REFERENCE_LIST
type fields, you must select a state-based or stateless record type to refer
to. You can also enter an optional back-reference field to create a link from
the referenced record to this field record.
- SHORT_STRING
- A variable-length character string with a 254-character maximum. You
set the length in the Properties window when defining the field. Enter a value
between 1 and 254 in the Maximum Length field. When a user enters a value
in a field of the type SHORT_STRING, any leading or trailing spaces are removed.
- DBID
- Reserved for system fields.
- ID
- Reserved for system fields.
- JOURNAL
- Reserved for system fields.
- STATE
- Reserved for system fields.