Retrieve and Update errors and the DBError event – PB Docs 126

Retrieve and Update errors and the DBError event

Retrieve and update testing

When using the Retrieve or Update method in a DataWindow control,
you should test the method’s return code to see whether
the activity succeeded.

note.png Do not test the SQLCode attribute

After issuing a SQL statement (such as CONNECT, COMMIT, or DISCONNECT)
or the equivalent method of the transaction object, you should always
test the success/failure code (the SQLCode attribute in
the transaction object). However, you should not use
this type of error checking following a retrieval or update made
in a DataWindow.

For more information about error handling
after a SQL statement, see:

Table 2-4: Return codes for the Retrieve and Update methods

Method

Return code

Meaning

Retrieve

>=1

Retrieval succeeded; returns the number
of rows retrieved.

-1

Retrieval failed; DBError event triggered.

0

No data retrieved.

Update

1

Update succeeded.

-1

Update failed; DBError event triggered.

Example

PowerBuilder

If you want to commit changes to the database only if an update
succeeds, you can code:

Web ActiveX

To commit changes to the database only if an update succeeds, you
can code:

Using the DBError event

The DataWindow control triggers its DBError event whenever
there is an error following a retrieval or update; that is, if the
Retrieve or Update methods return –1. For example, if you
try to insert a row that does not have values for all columns that
have been defined as not allowing NULL, the DBMS rejects the row
and the DBError event is triggered.

By default, the DataWindow control displays a message box
describing the error message from the DBMS, as shown here:

udwo07.gif

In many cases you might want to code your own processing in
the DBError event and suppress the default message box. Here are
some tips for doing this:

Table 2-5: Tips for processing messages from DBError event

To

Do this

Get the DBMS’s error code

Use the SQLDBCode argument of the DBError event.

Get the DBMS’s message text

Use the SQLErrText argument of the DBError event.

Suppress the default message box

Specify an action/return code
of 1.

note.png About DataWindow action/return codes

Some events for DataWindow controls
have codes that you can set to override the default action that
occurs when the event is triggered. The codes and their meaning
depend on the event. In PowerBuilder, you set the code with a RETURN
statement. In the Web ActiveX, you call the SetActionCode or setActionCode
method.

Example

PowerBuilder

Here is a sample script for the DBError event:

During execution, the user would see the following message
box after the error:

udwo08p.gif

Web ActiveX

In JavaScript, the code for the DBError event might look like this:


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