Query execution time issue - php

Question

I have some trouble with the execution time of a script. The query takes a lot of time. This is the query:
select avg(price) from voiture where duration<30 AND make="Audi" AND model="A4"
+---+---+---+---+---+---+---+---+---+---+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+---+---+---+---+---+---+---+---+---+---+
| 1 | SIMPLE | voiture | ALL | NULL | NULL | NULL | NULL | 1376949 | Using where |
+---+---+---+---+---+---+---+---+---+---+
select price from voiture where duration<30 AND make="Audi" AND model="A4"
+---+---+---+---+---+---+---+---+---+---+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+---+---+---+---+---+---+---+---+---+---+
| 1 | SIMPLE | voiture | ALL | NULL | NULL | NULL | NULL | 1376949 | Using where |
+---+---+---+---+---+---+---+---+---+---+
This query take around 2 seconds to be executed on the phpMyAdmin interface. I tried to see what the issue was and removing the avg function makes the query lasts around 0.0080 seconds.
I asked myself how long it would take to make the calculate the avg in the php script, but the query with or withouth avg takes around 2 seconds both.
So I decided to take all the values of my table and make the process in the script, so I use this query:
select * from voiture where duration<30 AND make="Audi" AND model="A4"
+---+---+---+---+---+---+---+---+---+---+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+---+---+---+---+---+---+---+---+---+---+
| 1 | SIMPLE | voiture | ALL | NULL | NULL | NULL | NULL | 1376949 | Using where |
+---+---+---+---+---+---+---+---+---+---+
On the phpMyAdmin interface, it takes 0.0112 seconds. But in my php script, it takes 25 seconds !
$timestart2=microtime(true);
$querysec='select * from voiture where duration<30 AND make="Audi" AND model="A4"';
$requestsec=mysql_query($querysec) or die(mysql_error());
$timeend2=microtime(true);
$time2=$timeend2-$timestart2;
$page_load_time2 = number_format($time2, 9);
Here is the table structure:
CREATE TABLE `voiture` (
`carid` bigint(9) NOT NULL,
`serviceid` bigint(9) NOT NULL,
`service` varchar(256) NOT NULL,
`model` varchar(256) DEFAULT NULL,
`gearingType` varchar(256) DEFAULT NULL,
`displacement` int(5) DEFAULT NULL,
`cylinders` int(2) DEFAULT NULL,
`fuel` varchar(32) DEFAULT NULL,
`mileage` int(7) DEFAULT NULL,
`existFlag` tinyint(1) DEFAULT NULL,
`lastUpdate` date DEFAULT NULL,
`version` varchar(256) DEFAULT NULL,
`bodyType` varchar(256) DEFAULT NULL,
`firstRegistration` date DEFAULT NULL,
`powerHp` int(4) DEFAULT NULL,
`powerKw` int(4) DEFAULT NULL,
`vat` varchar(256) DEFAULT NULL,
`price` decimal(12,2) DEFAULT NULL,
`duration` int(3) DEFAULT NULL,
`pageUrl` varchar(256) DEFAULT NULL,
`carImg` varchar(256) DEFAULT NULL,
`color` varchar(256) DEFAULT NULL,
`doors` int(1) DEFAULT NULL,
`seats` int(1) DEFAULT NULL,
`prevOwner` int(1) DEFAULT NULL,
`co2` varchar(256) DEFAULT NULL,
`consumption` varchar(256) DEFAULT NULL,
`gears` int(1) DEFAULT NULL,
`equipment` varchar(1024) NOT NULL,
`make` varchar(256) NOT NULL,
`country` varchar(3) NOT NULL
)
There's an index on carid and serviceid
Why does my query takes so long to be executed ? Is there a way it can be improved ?
Why is the execution time different from phpMyAdmin and my php script ?

Answer 1

On the phpMyAdmin interface, it takes 0.0112 seconds. But in my php
script, it takes 25 seconds!
phpMyAdmin interface adds LIMIT to each query. By default it's LIMIT 30.
To decrease time of your aggregate query you need to create indexes for each condition you use(or one composite index, may be).
So, try to create indexes for your model, make and duration fields.
Also, your table is too denormalized. You can to create pair of table to normalize it for a bit.
Ex: Vendors(id, name), Models(id, name) and modify your voiture to have vendor_id/model_id fields instead of text make/model.
Then your initial query will look like:
select avg(t.price) from voiture t
INNER JOIN Models m ON m.id = t.model_id
INNER JOIN Vendors v ON v.id = t.vendor_id
where t.duration<30 AND v.name="Audi" AND m.name="A4"
It will scan light lookup tables for text matches and operate with your heavy table with indexed ids.

Answer 2

There are many possible solution, first thing you can do is create index at DB level this can also improve your execution time.
second this check server, there may be some processes which would occupying your server resources, and making your server slow.

Answer 3

You can make it faster using GROUP BY like
select AVG(price) from voiture where duration<30 AND make="Audi" AND model="A4" GROUP BY make
Also you can add an index for make column
ALTER TABLE `voiture` ADD INDEX `make` (`make`)