db.reader

function

Library: Database access (OMDB)
Import : omdb.xmd

Returns: requested field data as a source

Declaration

define external string source function db.reader of   value db.field  field null value string   null
        optional

Argument definitions

field: is a db.field object associated with a field in the current record in an active SQL query record set.

null: is an optional string that will be returned instead of a zero-length string when the field value is NULL.

Purpose

The db.reader function returns the requested field data as an OmniMark source.

Requirements

The database connection represented by db.database must be:

open (else external exception OMDB209)
in scope (else external exception OMDB103)

The db.field object field must be associated with a query (else external exception OMDB302).

The data cursor must be positioned on an existing row (else external exception OMDB205).

Usage Notes

To avoid external exception OMDB205, use the db.record-exists function to verify that the row exists prior to retrieving a field value.

If the record has a date, time, or timestamp field, the field's value will be formatted in the OmniMark Date and Time library format. (This format returns the time with a time zone offset from UTC time, which most databases do not provide.)

If the field value is NULL, this function returns either an empty string or a string specified as argument null. The argument null, if it is used, should be outside of the normal range of field values. If no such value exists, it is safer to use db.is-null function instead.

Example

        repeat
           exit unless db.record-exists my-query
  
           repeat over my-query
              output db.reader of my-query
                 null '-DNF-'
              output '%t' unless #last
           again
           output '%n'
  
           db.move-record my-query
         again

Related Topics

Other Library Functions