In the last episode (May 08), Nitin Nanivadekar said:
> i am using mysql 3.23 on a machine with 150MB HDD and 96 MB ram. i've
> already mailed you about some problems regarding mysqld functioning.
> now i am getting a serious problem.
> 1. the max () keyword reports 'different' resultsets
> when following queries are sent to it,
> a. select max(id) from table1;
> b. select max(id) from table1 where id2=100;
> in any condition (like the low resources etc.) i should not get
> different results from seemingly identical queries.
Those queries are not identical. What if your table looks like this:
id | id2
1 | 100
2 | 99
Query a) will return 2, query b) will return 1.
> 2. i will also point one observation when i was
> hacking the max () function. when there is an empty
> set max() reports Null. this makes max() limited to
> arithmatic ops only. i am using max() to find the next
> incremental primary key index for some other table.
> i am now seriously considering NOT using max() for
> that reason after 1,. and 2. above.
When there is an empty set, what can max() possibly return except NULL?