Chapter 1-3: Data Dictionary |
Fields and Field Types Fields represent the smallest units of data storage in an APPX application. Each field contains an item of information in a database. While a domain establishes a set of common attributes (such as required physical storage space) for one or more fields, it is the field that is used to store application data. The data information stored in a field is referred to as a field value. Fields are grouped together as records stored within files. There are thirteen types of fields in the APPX data dictionary: Domain fields are fields that directly express the attributes defined in a domain while they define and occupy new physical space in a file. There are nine distinct domain-type fields: Alpha, Format, System, Text, Token, Date, Logic, Numeric, and Same As. Refer to the Domains and Domain Types section for additional information. You can choose to set up physical fields to exclusively reference domains, or you can set up individual field types directly. Alpha fields are comprised of numbers, letters, and special characters (-, #, or &, for example). Format fields are like alpha fields except that an edit mask is the primary characteristic. System fields, often referred to as audit fields, display data that is provided by the system. Text fields allow the user to enter blocks of text on the data entry screen. Token fields are like alpha fields, except that they have specific values that are stored as corresponding numbers. Numeric fields are restricted to number, decimal (.), and sign (-) entries. Date fields are patterns for fields that contain dates and/or times, from centuries through hundredths of a second. Logic fields are fields with possible values of yes Synonym fields provide alternative names for referencing existing APPX fields. They occupy no physical space in a file aside from the fields they reference. Substring fields represent discrete portions of longer alphanumeric fields. They occupy no physical space in a file aside from the fields they are a part of. Group header fields are used to group other fields by identifying the beginning and ending fields in a group of fields. The group can then be referenced by the name of the group header field. Group headers occupy no physical space in a file aside from the fields that comprise the group. Group trailer fields are optional placeholders to allow for terminating a group without referencing a physical field. They provide a streamlined method to allow for additions to the end of groups. They also provide visual clues as to the ends of groups when scanning the Data Dictionary. Group trailers occupy no physical space in files. |
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or no 
, or 
to represent an unknown value (Y, N, or blank using Character Mode).