Field Lengths

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Field Lengths

The length of fields in an EQuIS database have been defined in advance as part of the database schema as well as by the datatype used. Fields that allow text (typically using the varchar datatype) are limited in length based on the field type; remark fields might allow 1,000 characters or more, code fields used as reference values might allow 2-4 characters, and name fields might allow 20-40 characters. EDD formats also use predefined field lengths that relate to those used by the database or an associated schema.

 

The two primary purposes for limited length in reference values (in many systems called “codes”) are to:

control input - i.e. must match a predefined value

provide an abbreviation that defines the item (e.g. person's initials vs. their full name)

 

This abbreviation is beneficial for multiple reasons:

makes data entry easier/faster

allows abbreviated reporting (can be easier to read and evaluate)

reduces size of the tables and indexes

improves performance

 

The abbreviated value could be a system-generated ID; however, learning/memorizing IDs is impractical and generally still begs for an abbreviated text (like a person's initials). In early computer programs, these abbreviated values/codes were usually between 3-10 characters; however, over the years, they have been lengthened.

 

At some point, the increased size diminishes/eliminates the value of the abbreviation - in most cases, 10-20 characters suffices, and much longer than that becomes too long. In designing EQuIS, the purpose and needs of each reference value are considered, and effort is made to ensure that they are sufficiently long while maintaining the value of abbreviation. Those that are longer have generally come to that point because of a specific need.