Which command raised the exception? - oracle

Question

Is there a variable like SQLERRM or SQLCODE that holds the statement which raised the error?
example:
/*
if some error raised from this code
and I want to know which statement cause the failure..
I wish to use some oracle varaible to know it
*/
begin
select * from t1;
select * from t2;
exception when others
dbms_output.put_line(sqlerrm || ' raised from this statement:' || <some_variable>;
end;
-- excepted result: no data found raised from this statement: select * from t2

Answer 1

Simple answer, no. You're losing some information by defining an exception handler. With an unhandled exception you'd get an error message which includes the line number. But obviously we need to handle errors, log them, etc. So not having a line number is pretty rubbish.
Fortunately there are a couple of options. In older versions of Oracle we can use dbms_utility.format_error_backtrace() and dbms_utility.format_error_stack() to get some useful information, including the line numbers. It's pretty unwieldy and (especially for the backtrace) verbose.
In Oracle 12c we got a whole package devoted to PL/SQL call stack: UTL_CALL_STACK. It is a box of bits and requires more than one call to get things but we can retrieve a specific line number with unit_line(). Tim Hall has written a typically fine introduction to the new feature. Find out more.
The other thing to consider is how good program design can resolve this problem. Specifically the Single Responsibility Principle. This is a fundamental guideline of program design: a program unit should do one thing. If we asking the question "which command through this error" it can be a sign that we're violating the SRP.
Let's resign your code so it follows this design principle:
declare
type nt1 is table of t1%rowtype;
type nt2 is table of t2%rowtype;
l_t1 nt1;
l_t2 nt2;
x_t1_ndf exception;
x_t2_ndf exception;
function get_t1 return nt1 is
return_value nt1;
begin
select *
bulk collect into return_value
from t1;
if return_value.count() = 0 then
raise x_t1_ndf;
end if;
return return_value;
end get_t1;
function get_t2 return nt2 is
return_value nt2;
begin
select *
bulk collect into return_value
from t2;
if return_value.count() = 0 then
raise x_t2_ndf;
end if;
return return_value;
end get_t2;
begin
l_t1 := get_t1;
l_t2 := get_t2;
exception
when x_t1_ndf then
dbms_output.put_line('T1 has no data');
when x_t2_ndf then
dbms_output.put_line('T2 has no data');
end;
Obviously more typing than your original code but partly that's because this toy is complete working code, unlike the code you posted. Also in real life these modules would be discrete units, rather than private functions in an anonymous block, and so we could re-use them in multiple other programs.
Also dbms_output.put_line() is not the proper way to handle exceptions, but I've left that because it's what your code does.

Answer 2

There is no built-in that you can use for that.
One way could be by handling the exceptions of the single statements, with something like (pseudo-code):
declare
err varchar2(100);
myException exception;
begin
...
begin
select * from t1;
exception
when others then
err := 'Error in select * from t1: ' || sqlerrm;
raise myException
end;
begin
select * from t2;
exception
when others then
err := 'Error in select * from t2: ' || sqlerrm;
raise myException
end;
...
exception
when myException then
dbms_output.put_line(err);
when others then
dbms_output.put_line('Unhandled exception: ' || sqlerrm);
end;
For something more, this can be very useful.

Answer 3

Using a single exception handler for multiple statements always mask
the statement that caused an error.
Instead, you can use a Local variable(Locator) to track statement execution, as follows:
DECLARE
err_stmt NUMBER:= 1; -- Indicates 1st SELECT statement
BEGIN
SELECT ... -- Statement 1
err_stmt := 2; -- Indicates 2nd SELECT statement
SELECT ... -- Statement 2
EXCEPTION
WHEN OTHERS THEN
dbms_output.put_line(sqlerrm || ' raised from this statement number:' || err_stmt;
END;
Cheers!!