当我尝试在 oracle sql 中执行我的过程时出现“光标已打开”错误

Question

I wrote a function in oracle sql to fetch the name of an employee whose id in the table matches the input given to the function.

 create or replace function id_search
    (
    x in number
    )
    return number
    is
    cursor e is select ename from employee where emp_id = x;
    begin
    open e;
   for i in e
   loop
   dbms_output.put_line('name is :'||i.ename);
   end loop;
   close e;
   return 0;
   end;
   /

After this, I called this function in a procedure I had written:

SQL>     create or replace procedure id_searchP
  2      (
  3      y in number
  4      )
  5      is
  6      t number:= 1;
  7      begin
  8      t := id_search(y);
  9      end;
 10      /

However, when I try to execute my procedure, I am encountering the error:

SQL> exec id_searchP(2);
BEGIN id_searchP(2); END;

          *

ERROR at line 1:
ORA-06511: PL/SQL: cursor already open
ORA-06512: at "tom.ID_SEARCH", line 7
ORA-06512: at "tom.ID_SEARCH", line 10
ORA-06512: at "tom.ID_SEARCHP", line 8
ORA-06512: at line 1

why Am I getting this error?

Answer 1

You are opening and closing the cursor two times. You do not need to open e; and then again for i in e . Do i like this in your function:

create or replace function id_search(x in number)
return number
is

    cursor e 
    is
    select ename 
    from employee 
    where emp_id = x;

begin

       for i in e loop
          dbms_output.put_line('name is :'||i.ename);
       end loop;

       return 0;
end;

Then the procedure is ok:

create or replace procedure id_searchP(y in number)
is
     t number:= 1;
begin
     t := id_search(y);
end;

And then only one call will be enough:

BEGIN 
  id_searchP(2); 
END;

Here is the DEMO

Answer 2

You are encountering this issues because you are explicitly opening cursor e, and then attempting to start a cursor for loop on cursor e. However, the cursor for loop implicitly attempts to open cursor e, which you already explicitly opened.

If you want to use a cursor for loop you will need to remove your explicit open and close statements.

Answer 3

There are very few times when you need to use an explicitly-declared cursor. Get in the habit of using cursor FOR-loops:

 create or replace function id_search(pinEmployee_ID in number)
    return number
 is
 begin
   for rowEmployee in (select ename
                         from employee
                         where emp_id = pinEmployee_ID)
   loop
     dbms_output.put_line('name is :' || rowEmployee.ename);
   end loop;

   return 0;
 end id_search;

There - shorter, simpler, less error-prone, and easier to understand.

Please use meaningful names. I don't care if it's a school assignment or whatever - use meaningful names. Don't make people dig into your code to figure out what your parameters mean or are used for.

Further - please take the time to format your code so it's readable. Indent consistently, make sure that code levels are apparent to the naked eye, put whitespace in so your code can be read easily, spell things properly, and spell things out. I don't want to see i for a parameter name - if what's being passed in is (supposed to be) an employee ID, then make sure that the name of the parameter makes that apparent. Computer programming is primarily an exercise in communication - between you, the computer, and the poor dumb SOB who in ten years will have to read your code and figure out what it does. Don't be the guy that everyone cusses at when they have to maintain your code. Develop good habits now.

Programming is a craft. If this is something you really want to do, work on doing it well. Every assignment, every script, every day is an opportunity to improve. Or at the very least to show what you know. Make sure that what you show is your best, always.