A question about input values inside PL/SQL block

Question

Dear all,
I would appreciate if you could kindly help me with this question.
Consider the following code.
DECLARE
  myvar1 NUMBER;
  myvar2 NUMBER;
  myvar3 NUMBER;
BEGIN
  myvar1 := &1;
  myvar2 := &2;
  myvar3 := &3;
  DBMS_OUTPUT.put_line('myvar1 = ' || myvar1);
  DBMS_OUTPUT.put_line('myvar2 = ' || myvar2);
  DBMS_OUTPUT.put_line('myvar3 = ' || myvar3);
END;
/This program reads three values as input and prints them. However, I noticed that if instead of writing
myvar1 := &1;
myvar2 := &2;
myvar3 := &3;I write
myvar1 := '&1';
myvar2 := '&2';
myvar3 := '&3';The program will have very same result. I would like to know whether there is a semantic difference between both syntax,
that is, is there any difference between for example &myvar1 and 'myvar1'?
Thanks in advance,
Dariyoosh

Answer 1

Try this
CREATE TABLE test_sem  (x VARCHAR2(10), y NUMBER)
INSERT INTO test_sem VALUES ('A',1);
INSERT INTO test_sem VALUES ('B',1);
INSERT INTO test_sem VALUES ('C',1);
INSERT INTO test_sem VALUES ('D',1);
SELECT * FROM test_sem WHERE x='&1' --OK
SELECT * FROM test_sem WHERE x=&1 -- error not a valid number
SELECT * FROM test_sem WHERE y=&1 -- ok
SELECT * FROM test_sem WHERE y='&1' -- ok since numbers can be converted to strings'&1' is for characters &1 for numbers;
You can verify form above test case
Regards,
Bhushan