Auto sequencing

Question

Hi,
I am new to Oracle but have experience with the procedural languages in MS SQL Server and Sysbase and in the past have used these languages extensively.
I often use a number for my PK and get the database to increment that for me. In MS SQL Server you denote this field as [Identity=Yes] and you can set the seed (ie where to start the sequence) as well. Now in oracle as far as I can see I have to do this, as follows:
DROP SEQUENCE INDEM_SIGS_SEQ;
CREATE SEQUENCE INDEM_SIGS_SEQ MINVALUE 1 MAXVALUE 999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER NOCYCLE;
CREATE TABLE INDEMNITY_SIGNATORIES (
IS_NO NUMBER(6) NOT NULL ENABLE,
... more fields
CONSTRAINT PK_INDEMNITY_SIGNATORIES primary key (IS_NO),
CONSTRAINT ... more constraints
CREATE OR REPLACE TRIGGER BI_INDEM_SIGS
before insert on INDEMNITY_SIGNATORIES
for each row
begin
select INDEM_SIGS_SEQ.nextval into :NEW.IS_NO from dual;
end;
ALTER TRIGGER BI_INDEM_SIGS ENABLE;
Now this seems a long-winded way of doing something that in SQL Server I just need to change a property value to do. But fair enough I only have to do it once for each table that has a sequential prime key, but if anyone is looking at this and can think of an easier way then please let me know.
The next thing is that you sometimes get the situation when you insert a record and that you need the vaue of the prime key of the record you have just inserted. So you can then insert or update records in another tables that have this number possibly as a FK in other tables.
In SQL Server I would do this as follows:
INSERT INTO contacts (contact_type, first_name, surname, secretary, salutation, title, email, tel, mobile, fax, xmas_card, notes, created, modified)
VALUES (@contact_type, @first_name, @surname, @secretary, @salutation, @title, @email, @tel, @mobile, @fax, @xmas_card, @notes, GetDate(), GetDate());
SELECT contact_no FROM contacts WHERE (contact_no = @@IDENTITY);
I hope this is clear and that someone can help.

Answer 1

If you want the primary key column to be populated automatically, the trigger you've posted is correct. Lots of folks prefer just to put the sequence in the actual insert statement, i.e.
INSERT INTO indemnity_signatories( is_no, other_columns )
  VALUES( indem_sigs_seq.nextval, other_values );You can get that sequence value back either using the RETURNING clause or using the CURRVAL of the sequence, i.e.
INSERT INTO indemnity_signatories( other_columns )
  VALUES( other_values )
  RETURNING is_no INTO my_local_is_no_variable;or
SELECT indem_sigs_seq.currval
  INTO my_local_is_no_variable
  FROM dual;Justin