Two small corrections:
ad point 1.
"b in ('2004-05-01')" behaves different from "b = '2004-05-01'". The
last one is better: key_len = 6, instead of 3.
mysql> explain select count(*) from A, B where A.a=B.a and b ='2004-05-01';
+---+---+---+-+-+---+
Hello,
I reached a point I can't go any further with forcing mysql to use the
index as much as needed. I am facing a multi column index of which only
the first column is used.
Let me explain...
This works fine:
create table A ( a mediumint not null, b date not null, index (a,b));
Populate the
