Creating triggers

Complete these instructions to create a trigger.

1. Write a FlashBASIC subroutine with this general outline. Note the ACCESS () function is functional at the file-level, that is, when the subroutine is defined as part of the correlative of a file-defining item. The functionality of the ACCESS function in the instance is different from that described in Correlatives.

   subroutine subname(record)
      * "record" contains list of columns separated by
      * 0xFE characters (minus the primary key).
      * To get the primary key, use the access(10)
      * function.
      primarykey = access(10); 
   
      * Do any desired trigger processing
      * When complete, the resulting record may be
      * modified by modifying the "record" variable.Record = …
    
   
      * If the update should fail due to an integrity
      * violation or some other reason, then the
      * "inputerr" statement displays an error message
      * and rolls back ALL updates in the current
      * transaction. 
   
      if update.fails then inputerr 'Error Message' 
   
   return

2. Compile the program using the compile TCL command.
3. Attach the program to the D3 file with the callx trigger. To do this:

   • Log to the account where the D3 file corresponding to the SQL table exists.

   • Enter ud file_name

   • Due to SQL naming conventions, the D3 filename, file_name, may not be the same as the SQL tablename.

     Note that the older ed editor can be used if you are more comfortable with that editor.

   • If using the ud command, press <Return> several times until the cursor is on the row marked correlative.

   • Entercallx account, file, subroutine_name

   • where account and file are the account and file where the FlashBASIC program resides, and subroutine_name is the name of the program.

   • Press CTRL-X followed by the F key to file, or apply, the changes.

   With the trigger in place, any database update, whether from SQL or from a legacy application, will result in a call to the applied code.

   Note: If using transactions with D3 SQL statements, the trigger is not called until after a COMMIT. Therefore, errors returned by a callx trigger are not reported until after the transaction is committed.