Writing a oracle stored procedure to generate a unique serial number?

Question

I need to generate a unique serial number in our web application.

I have created a table called SerialNumber which will have only one row. In the begining it will have value like '0000000000' ten times zero. This will be incremented by one every time a serial number needs to be generated.

e.g. 0000000001, 0000000002 and so on.

I have kept the column datatype as Integer which stores values as 0, 1, 2 etc and not as 0000000001. I want the serial number to be ten digits only with zeros appended at the begining.

Please help me to write the stored proc for this.

Answer 1

select to_char(<column-value>, 'FM0000000000') from serialNumber;

I don't know what's behind your requirement, but most probably, you are better served with a sequence. Using a table to generate unique ids is usually a poor choice that should be reviewed.

As for a stored procedure along with a sequence, a basic frame to build upon could be:

The sequence:

create sequence serial_number_seq;

The stored procedure (actually: a function)

create or replace function next_serial_number return varchar2 as

       serial_number_ number;
       MAX_SR_NO number;
begin

       select serial_number_seq.nextval into serial_number_ from DUAL;

       Select MAX(sr_no) INTO MAX_SR_NO from serialNumber;

       serial_number_ := GREATEST(serial_number_, MAX_SR_NO); 

       return to_char(serial_number_, 'FM0000000000');

end    next_serial_number;
/

testing

begin
  dbms_output.put_line(next_serial_number);
  dbms_output.put_line(next_serial_number);
  dbms_output.put_line(next_serial_number);
  dbms_output.put_line(next_serial_number);
  dbms_output.put_line(next_serial_number);
  dbms_output.put_line(next_serial_number);
-- in the place where you use the serial number the greatest 
--  of inserted value from external system or sequence value will be used
 final_value:= next_serial_number;
end;
/