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

Return type: Source Returns:  Requested field data as a source.

Declaration

  define external source function db.reader
    of   value db.field  field
    null value stream   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.

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 you specify for null within the function call.

Example

        repeat
           exit unless db.record-exists my-query

           repeat over my-query
              output db.reader of my-query
                 null '-dnf-'
              output '%t' when ! #last
           again
           output '%n'

           db.move-record my-query
         again

Related Syntax    db.query    db.move-record    db.record-exists    db.field

Related Concepts    Using the OMDB library

Other Library Functions    db.advance-recordset    db.close    db.commit    db.compile-statement    db.database    db.delete    db.discard    db.execute    db.execute-in    db.field    db.insert    db.move-record    db.omdb-version    db.omdb-version-oci8    db.omdb-version-oci8i    db.omdb-version-odbc    db.open-oci8    db.open-oci8i    db.open-odbc    db.open-procedure    db.open-table    db.prepare    db.procedure    db.query    db.reader    db.record-exists    db.rollback    db.set-transaction-type    db.statement    db.streaming-execute    db.table    db.update    db.writer

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