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

Purpose

The db.field OMX component allows you to access the data value that exists within a row of a database record set field. This OMX component is a shelf, where each field value is placed in a separate item on the shelf, and each item key is the unique name of the field. Use the db.field OMX component in conjunction with db.database to create a connection to a database and obtain a read-only set of data from that database.

Usage Notes

Within your program, you can create as many instances of the db.field OMX component as you require by declaring global and local shelves of type "db.field". These shelves must be declared as variable.

When you use the db.query, db.execute or db.streaming-execute functions, the db.field shelf is automatically bound to the record set created by the specified SQL query. When you move the data cursor in the record set using the db.move-record function, the db.field shelf is automatically repopulated with whatever values are in the current row. You retrieve values from the db.field OMX variable with the db.reader function.

Please refer to OMX Components for a general description of OMX components and how they are used.

Related OMDB library functions

The functions

• db.query - execute an SQL query on the specified database.
• db.execute - execute a stored procedure or compiled statement. (Must be a query.)
• db.streaming-execute-execute a streaming compiled statement.(Must be a query.)

• db.reader and db.is-null - retrieve the value of the specified field for the current row of the result set.
• db.record-exists - check whether the data cursor is positioned on an existing row or not.
• db.move-record and db.move-dynamic-record - change the position of the data cursor within the specified record set.
• db.advance-recordset - test for and move to another result set.

Example

Once you have declared your db.field OMX shelves, you can use those variables in the db.query, db.execute and db.streaming-execute functions that are part of the OmniMark Database library. For example:

  import "omdb.xmd" prefixed by db.
  
  process
     local db.database my-database
     local db.field my-query variable
  
     local stream SQL-query initial
     {  "select C.CourseName, S.StudentName, SC.Grade " ||
        "from Student S, Course C, StudentCourse SC " ||
        "where SC.CID = C.CID and S.SID = SC.SID "
     }
  
     set my-database to db.open-odbc "MyDatabase"
  
     db.query my-database SQL sql-query into my-query
  
     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 Syntax    db.query    db.move-record    db.record-exists    db.reader    db.field    db.is-null

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.document-writer-sedna    db.execute    db.execute-in    db.field    db.insert    db.is-null    db.move-dynamic-record    db.move-record    db.omdb-version    db.omdb-version-oci10g    db.omdb-version-oci11g    db.omdb-version-oci8i    db.omdb-version-oci9i    db.omdb-version-odbc    db.omdb-version-sedna    db.open-oci10g    db.open-oci11g    db.open-oci8i    db.open-oci9i    db.open-odbc    db.open-procedure    db.open-sedna    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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