start and stop element in mysql

Question

Is there a way to setup an start or stop element in mysql ? I want to to select every element starting with id = 20 and stops when level < 3 the first time.

Answer 1

In mysql I think this is hard to do in one query, I thnk youd have to do something like

SELECT @ordernr = MIN(ordernr)
FROM ...
WHERE id = 20
AND    level < 3

If you have the id=20 rows:

ordernr level 
1        34
2        23
3        88
4        2   <- it will return 4
5        12
6        22
7        2

Then use the result:

SELECT ...
FROM ...
WHERE id = 20
AND ordernr <= @ordernr

It will return ordernr level 1 34 2 23 3 88 4 2

Answer 2

SQL doesn't offer conditions like you are asking for. It might be easiest to simply SELECT * and do the filtering in code.

As long as you don't ORDER BY or something else that requires the entire result set to be fetched all at once, this should perform reasonably well; you stop processing after finding your first level < 3 and then the zillions of other possible results behind that are never fetched.