Considerations for selecting field data types

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 File > Test Work 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 File > Test Work, 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.