RE: automatically incrementing an int value

[Paul DuBois]

At 11:09 -0500 3/10/03, Douglas B. Jones wrote:
Hi,

Great! This works, I did not use the 'null' and that is
where I had a problem. One other questions: is this atomic?
If I have several processes trying to do this at one time,
will each one correctly update the table (assuming they have
the same 'name' value.
Yes.

 Also, in the part: unique (name(100)),
what does the 100 do here? Is that saying the first 100 chars
are considered unique?
Exactly.

Thanks,
Cheers,
Douglas
 -----Original Message-----
 From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
 Sent: Monday, March 10, 2003 10:36 AM
 To: Douglas B Jones
 Cc: [EMAIL PROTECTED]
 Subject: Re: automatically incrementing an int value


 As I read the manual, the REPLACE command will do what you want.

 Make the name field UNIQUE, and the number field AUTO_INCREMENT NOT NULL.
 Replace dos a delete-if-present, insert. The insert generates a new ID.
 See test below, and note two rows affected by second replace.

 mysql> create table test (a int auto_increment not null, name tinytext not
 null, primary key (a), unique (name(100))) ;
 Query OK, 0 rows affected (0.02 sec)
 mysql> replace into test values (null, "hello") ;
 Query OK, 1 row affected (0.01 sec)
 mysql> select * from test ;
 +---+-------+
 | a | name  |
 +---+-------+
 | 1 | hello |
 +---+-------+
 1 row in set (0.01 sec)
 mysql> replace into test values (null, "hello") ;
 Query OK, 2 rows affected (0.02 sec)
 mysql> select * from test ;
 +---+-------+
 | a | name  |
 +---+-------+
 | 2 | hello |
 +---+-------+
 > 1 row in set (0.00 sec)


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