I don't think MySQL has exactly what you are looking for, but you may be able
to get the behavior you want.
The auto_increment value is actually based on an index and doesn't have to be unique. So you could create a compound index that has
one or more fields plus the auto_increment field. The effect would be having multiple sequence numbers.
CREATE TABLE competenza (
competenza varchar(30) NOT NULL default 'comp-06-',
id_competenza int unsigned not null auto_increment,
descrizione varchar(100),
PRIMARY KEY (competenza, id_competenza)
)
Since your PRIMARY KEY is a combination of 2 fields (competenza + id_competenza ), each competenza value will have it's own auto
increment (id_competenza ) sequence. So id_competenza won't be unique, but the combination of competenza + id_competenza will be.
----- Original Message -----
From: "Luca Ferrari" <[EMAIL PROTECTED]>
To: <mysql@lists.mysql.com>
Sent: Tuesday, January 02, 2007 8:54 AM
Subject: sequences and auto_increment
Hi all,
I'm new to MySQL coming from PostgreSQL backgroud. I'd like to know how to
obtain the same effect of a sequence + concat as default value of a table in
mysql. For example, consider the following table definition:
CREATE TABLE competenza
(
id_competenza character varying(30) NOT NULL DEFAULT ('comp-06-'::text ||
(nextval('sequenza_competenza'::regclass))::text),
descrizione character varying(100),
CONSTRAINT competenza_pkey PRIMARY KEY (id_competenza)
)
there, id_competenza is compound by a string "comp-06" and the next value of a
sequence (similar to auto_increment). In MySQL there're no sequences, or
better, there's only an auto_increment action on an int field. How can I
obtain the same effect of the concatenation of a sequence and a string?
Thanks,
Luca
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