Display an Alert message from PL/SQL block in APEX

Question

Hi,
we are getting an oracle exception while inserting a new row. As it is having the unique constaint on a coulumn.
Now the problem iis we need to Display an "Alert message" based on the input field validation. That java script code for alert has to be embeded nside a PL/SQL block in Oracle APEX Application.
we tried doing this with below code:
Begin
INSERT INTO <<table name>>(ID,NAME) VALUES (s1,:TXT_s2);
exception when others then
htp.p('<script language="javascript">');
htp.p('alert("Exception");');
htp.p('</script>');
end;
If anybody knows .... please reply.
Thanks,
Subarna

Answer 1

If your end goal is showing a pretty error message instead of the message that the tables unique constraint raises try the following. This logic will show a nice message and not try to insert non-unique data.
(1) Create a validation of type "Function Returning Error Text".
(2) Place similar code like the following in your validation. Notice that if the unique name does not exist the no_data_found returns null allowing the validation to pass.
DECLARE
  v_error varchar2(100);
BEGIN
  SELECT 'A person by this name already exists.'
  INTO v_error
  FROM your_table
  WHERE your_name = :P1_YOUR_NAME;
  RETURN v_error;
EXCEPTION
  WHEN no_data_found THEN
    RETURN NULL;
END;