Generate an unique number without sequence

Question

Hello,
I need generate an unique number without sequence. I am using Oracle 11.2, here is the details. The column idSeq is unique withing one specific idType. I don't want a sequence for each idType.
create table tb_test (idSeq number(5), idType number(5), addr varchar2(256));
insert into tb_test
(select case when idSeq is null then 1 else max(idSeq)+1 end, 3, 'Main street');
I am having ORA-00937 : not a single-group group function error, any suggestion?
Edited by: 939569 on 13-Feb-2013 11:21 AM

Answer 1

Hi,
939569 wrote:
Hello,
I need generate an unique number without sequence. Explain what you're trying to do, and why a sequence won't do it.
I am using Oracle 11.2, here is the details. The column idSeq is unique withing one specific idType. I don't want a sequence for each idType.
create table tb_test (idSeq number(5), idType number(5), addr varchar2(256));
insert into tb_test
(select case when idSeq is null then 1 else max(idSeq)+1 end, 3, 'Main street');
I am having ORA-00937 : not a single-group group function error,Right. Since the sub-query is using an aggregate function (MAX), everything in the SELECT clause must be an aggregate, a group by expression, a constant, or something that depends entirely on them. In this example, the CASE expression depends on idSeq, which is not an aggregate, not a group by expression (there is no GROUP BY clause) and not a constant.
Also, the sub-query must have a FROM clause. All queries and sub-queries in Oracle require a FROM clause.
any suggestion?Use a sequence. The numbers won't be consecutive within each idType, but what does that matter? Chances are, no matter what you do, you won't be able to maintain consecutive numbers within each idType anyway.
If you won't use a sequence, then you can try:
INSERT INTO  tb_test (idSeq, idType, addr)
SELECT  1 + NVL ( MAX (id_seq)
              , 0
,       3
,     'Main street;
FROM     tb_test
WHERE   idType  = 3
;