Ora 06533: Subscript Beyond Count

The array_var.extend portion of the code needs to be inside the loop. Each time you add to it, you are allocating new memory. Skipping this step is asking the code to store something without giving it space.

declare
  type salaryvarray is varray(6) of customers.salary%type;
  salary_array salaryvarray:=salaryvarray();
  c_salary customers.salary%type;
  i integer(2);
  counter number(2);
begin
  select count(*) into counter from customers;
  for i in 1..counter loop
    salary_array.extend; -- Extend for each value.
    select salary into c_salary from customers where id =i;
    salary_array(i):=c_salary;
  end loop;
end;
/

You will very likely run into a similar error soon, however, ORA-06532: Subscript outside of limit. You limit your VARRAY to 6 elements, but customers could potential have more. Consider limiting the return, expanding the VARRAY or implementing a more dynamic collection type.

Your select count(*) into counter from customers; has more than 6 results this way not able to save into varray(6) variable.

Instead of array, that has a fixed number of elements, you can use nested table or associative array.

Source: Declare dynamic array in PLSQL

salary_array.extend just extend 1 index. In Your case You must use this syntax for extend all index of varray:

salary_array.extend(6);

for other case use size of varray insted of 6 .

Your salary_array can hold a maximum of 6 customer's salary, but your select count(*) into counter from customers returns more than 6 records.

Due to this the array is not able to hold the data or to put in other words, An in-limit subscript was greater than the count of a varray.