Creating a sequence for a varchar2 field in Oracle

Question

I want to create a sequence for this varchar. It would have been easier had it been a number instead of varchar. In that case, I could do

seq_no := se

Answer 1

If you're able I'd actually use a virtual column as defined in the CREATE TABLE syntax. It makes it more easily extensible should the need arise.

Here's a working example.

SQL> create table tmp_test (
  2     id number(7,0) primary key
  3   , col1 number
  4   , seq varchar2(8 char) generated always as (
  5           'A' || to_char(id, 'FM0999999'))
  6      );

Table created.

SQL>
SQL> create sequence tmp_test_seq;

Sequence created.

SQL>
SQL> create or replace trigger tmp_test_trigger
  2    before insert on tmp_test
  3    for each row
  4  begin
  5
  6    :new.id := tmp_test_seq.nextval;
  7  end;
  8  /

Trigger created.

SQL> show errors
No errors.
SQL>
SQL> insert into tmp_test (col1)
  2   values(1);

1 row created.

SQL>
SQL> select * from tmp_test;

        ID       COL1 SEQ
---------- ---------- --------------------------------
         1          1 A0000001

Having said that; you would be better off if you did not do this unless you have an unbelievably pressing business need. There is little point to making life more difficult for yourself by prepending a constant value onto a number. As A will always be A it doesn't matter whether it's there or not.