Thank you very much for your understandable representation, Mr.PREDA
and Mr.Vegerin.
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MySQL wil only use one index per table in a query... this is why in
most cases a composite index will do better that a single column
index.
And for the second is true... this is leftmost rule...
You have an index on:
a, b, c
You gain indexes on:
a, b
a
But you will need to set up yourself an i
indices.
Regards, Cor
- Original Message -
From: "Gabriel PREDA" <[EMAIL PROTECTED]>
To: "Takanobu Kawabe" <[EMAIL PROTECTED]>
Cc:
Sent: Wednesday, June 21, 2006 8:47 AM
Subject: Re: About the leftmost index prefixes using nounique index
Basically i
Basically it says that if you have an index let's say INDEX_1 on columns:
INDEX_1 : a, b, c, d
MySQL will act as if you had setup indexes on:
INDEX_1_1 : a, b, c
INDEX_1_2 : a, b
INDEX_1_1 : a
A query like:
SELECT a FROM table_name WHERE a > 9; - will use the index
SELECT a, b, c FROM table_na
hello,
I want to know about the leftmost index prefixes using nounique index/
About the composite index using primary key, in the reference 7.4.5,
I can understand the following
