Oracle errors handling

问题:

I have such code:

DECLARE
  e_not_exist EXCEPTION;
  PRAGMA EXCEPTION_INIT(e_not_exist, -942);
  car_name VARCHAR2(20);
BEGIN
  select name_of_factory into car_name from car where car_id = 1;
  dbms_output.put_line(car_name);
EXCEPTION
  when e_not_exist then
    dbms_output.put_line('Table or view does not exist');
  when OTHERS then
    dbms_output.put_line(to_char(SQLCODE));
END;

Actually, my table name is CARS but not CAR. But oracle doesn't handle this exception and gives me an error ORA-00942: Table or view doesn't exist. How can I handle this exception?

回答1:

You can't do that with static SQL. The error is coming when the code is being compiled, not executed. Try this instead:

 execute immediate 'select name_of_factory from car where car_id = 1' 
                    into car_name ;

回答2:

An ORA-00942 error is generally going to be a compile time error. Oracle has to resolve the name(s) of the tables at compile time. Exception handlers will trap errors at runtime, not compile time.

If you used dynamic SQL, you can postpone the resolution of names to runtime at which point you can catch the exception, i.e.

SQL> ed
Wrote file afiedt.buf

  1  declare
  2    no_such_table exception;
  3    pragma exception_init( no_such_table, -942 );
  4    l_cnt integer;
  5  begin
  6    execute immediate 'select count(*) from emps' into l_cnt;
  7  exception
  8    when no_such_table
  9    then
 10      dbms_output.put_line( 'No such table' );
 11* end;
SQL> /
No such table

PL/SQL procedure successfully completed.

But that is not a sensible way, in general, to write stored procedures. Your procedures should know what tables actually exist and syntax errors should be identified and resolved during development, not at runtime.