Mysql auto-increment partially by today's date only - is this possible? - mysql

Question

I have a requirement to auto increment an integer which I need "for the day". This is used for box numbers for orders being sent out in a day through our client's e-commerce website.
For example, the first order today would contain the box number 01. The second order would contain 02. This would be incremented specifically by a trigger or some kind of automatic function, depending on the date.
What I have described is not my exact/full requirement but I would like to know how I can code the above in particular? So if we imagine a table like this:
myboxnumbers (boxid [auto increment], yyyymmdd-date, boxno)
I would like a function in Mysql (stored procedure) to 'give me the next increment of the box number for today').
E.g.
function generateBoxNoForToday() {
//1. Get today's date
//2. Check the latest boxno in the above table for today
//3. If no boxno yet for today, set $new-boxno = 1
//4. If there is a boxno, my new $new-boxno = boxno + 1
//5. INSERT INTO myboxnumbers (yyyymmdd-date, boxno) VALUES (today(), $new-boxno)
}
Please guide on how could I actually "do" this in Mysql? I suppose I'm too used to PHP so it's tempting to do it there :) but it makes sense that this is purely a database function and so I would like to do how to do this and the easiest route to take for such a function?
Many thanks!

Answer 1

It's not hard to put this into your insert statement for this table. As #AlmaDo pointed out, you need to lock the table and avoid the COUNT(*) operator, however.
Issue these three sql statements one after the other. Don't do anything else until you've issued all three, or your system may fail to scale up when you need it to.
LOCK TABLES myboxnumbers WRITE;
INSERT INTO myboxnumbers
(yymmdd_date, boxno)
VALUES
(TODAY(),
SELECT 1 + IFNULL(MAX(boxno),0)
FROM boxnumbers
WHERE yymmdd_date = TODAY()
);
UNLOCK TABLES;
To make this efficient, you need an index on (yymmdd_date,boxno).
To retrieve the just-inserted boxno value, you can do this immediately after your UNLOCK TABLES statement.
SELECT boxno FROM myboxnumbers WHERE boxid = LAST_INSERT_ID()