: Mittwoch, 28. Februar 2001 12:11
An: [EMAIL PROTECTED]
Betreff: Re: EXPLAIN with unexpected result.
Hi
Two points:
- Any multi column index a,b,c also indexes a and a,b
- In using an index, efficiency is important, and if you have two indexes
a,b,c and a,d,b , when you hit data
from columns a+b+d
Hi
Two points:
- Any multi column index a,b,c also indexes a and a,b
- In using an index, efficiency is important, and if you have two indexes a,b,c and
a,d,b , when you hit data
from columns a+b+d, the database engine has to work out if accessing the data from
a+b is more efficient
than
Hello,
I'm slightly stunned seeing a result from the EXPLAIN statement.
I have a table "T" with columns "a", "b", "c", "d" and a multi-column index
on (a, b, c)
I perform a query:
EXPLAIN SELECT * FROM T WHERE a = , d = , b =
The result tells me that MySQL is taking index (a, b, c). Why?
Fur
