Atomicity problem / question

[Lars]

Hi,

I need a way to read a numeric field and then increment it by one in such a
way that even if two users did this at the exact same time, they would still
each get their own unique value. I would prefer a method not requiring me
to lock the whole table.

What is the best way to accomplish this?

I am using MySQL 3.23.58 and I use an ISAM type database.

Thanks,
Lars

[Lars]

> "only a write lock" is a little like "only an atomic bomb".

A write lock prevents others from accessing AT ALL; a read
lock prevents others from writing. But what you need here is
a write lock.

Oh, I had that backwards. That may not work too well, then. Probably a
separate table to hold these unique numbers would be a better approach after
all, since it would not interfere with the access to the rest of the
settings in the table.

You also end up doing a lot of joins to get specific attributes
(if present) in specific variables.

Out of curiosity, could you elaborate on this?

A query for printing business cards with the keyword = value
organization might look like:

SELECT a.value, b.value, c.value, d.value, e.value, f.value, g.value
FROM addrbook a
LEFT JOIN addrbook b on a.personid = b.personid and b.attribute = 'Last
Name'
LEFT JOIN addrbook c on a.personid = c.personid and c.attribute = 'Work
Street Address'
LEFT JOIN addrbook d on a.personid = d.personid and d.attribute = 'Work
City'
LEFT JOIN addrbook e on a.personid = e.personid and e.attribute = 'Work
State'
LEFT JOIN addrbook f on a.personid = f.personid and f.attribute = 'Work
Zip'
LEFT JOIN addrbook g on a.personid = g.personid and g.attribute = 'Work
Phone'
WHERE a.attribute = 'First Name';

I got it. No, this is not at all what I use that kind of tables for. The
Item, Value approach I use only for storing settings & resources, etc.

Thanks,
Lars