The dba Library, Special Topics

Field Display Tags

heitml Field Display Tags can be used within the TABLE view as well as within the FORM view. They are used to show the contents of a record field, either as normal HTML or as an input field of a form. Which one is used is chosen automatically depending on the environment and action specified.

dba currently supports the following Field Display tags:

• <dbafi> shows an ordinary text field
• <dbatfi> shows an ordinary text field, together with its
       name and HTML TABLE formatting
• <dbaTextarea> shows a text area, useful for working
       with blobs or long text fields.
• <dbamailto> is used for text-field Email addresses.
       It is displayed as a mailto link.
• <dbalink> is used for text-field hot-links and is
       displayed as such.
• <dbacheckbox> shows a database field with only two
       valid values as a checkbox.
• <dbaSelect> and <dbaOption> shows a menu of selectable
       options, for fields with a discrete value range.

Interfacing with dba Pages

A dba page is driven by an action. Actions are passed in the URL as fields with the same name. An action is active if the corresponding field has a non-null value. For example: to call a page with action first, add ?first=t to the page.

Besides the action, a key designating a certain record is passed to a page in all fields named k.Fieldname. Therefore, if you have a dba page showing a relation with the key lastname, calling the page with ?display=t&k.lastname=Emmelmann will display the record with key value Emmelmann.

Using dba Tags on database tables

The dba application requires each database relation to have an unique key. It accesses the relation using SQL SELECT statements designed for direct access via an index on the key fields.