is there better way to do these mysql queries?

问题

Currently i have three different tables and three different queries, which are very similiar to each others with almost same joins. I was trying to combine all that three queries with in one query, so far not much success though. I will be very happy if someone has better solution or a direction to point. Thanks.

0.0013       
SELECT `ilan_genel`.`id`, `ilan_genel`.`durum`, `ilan_genel`.`kategori`, `ilan_genel`.`tip`, `ilan_genel`.`ozellik`, `ilan_genel`.`m2`, `ilan_genel`.`fiyat`, `ilan_genel`.`baslik`, `ilan_genel`.`ilce`, `ilan_genel`.`mahalle`, `ilan_genel`.`parabirimi`, `kgsim_ilceler`.`isim` as ilce, (
 SELECT ilanresimler.resimlink
 FROM ilanresimler
 WHERE ilanresimler.ilanid = ilan_genel.id LIMIT 1
 ) AS resim
FROM (`ilan_genel`)
LEFT JOIN `kgsim_ilceler` ON `kgsim_ilceler`.`id` = `ilan_genel`.`ilce`
ORDER BY `id` desc
LIMIT 30 
0.0006       
SELECT `video`.`id`, `video`.`url`, `ilan_genel`.`ilce`, `ilan_genel`.`tip`, `ilan_genel`.`m2`, `ilan_genel`.`ozellik`, `ilan_genel`.`fiyat`, `ilan_genel`.`parabirimi`, `ilan_genel`.`kullanici`, `ilanresimler`.`resimlink` as resim, `uyeler`.`isim` as isim, `uyeler`.`soyisim` as soyisim, `kgsim_ilceler`.`isim` as ilce
FROM (`video`)
LEFT JOIN `ilan_genel` ON `ilan_genel`.`id` = `video`.`id`
LEFT JOIN `kgsim_ilceler` ON `kgsim_ilceler`.`id` = `ilan_genel`.`ilce`
LEFT JOIN `ilanresimler` ON `ilanresimler`.`id` = `ilan_genel`.`resim`
LEFT JOIN `uyeler` ON `uyeler`.`id` = `ilan_genel`.`kullanici`
ORDER BY `siralama` desc
LIMIT 30 
0.0005       
SELECT `sanaltur`.`id`, `ilan_genel`.`ilce`, `ilan_genel`.`tip`, `ilan_genel`.`m2`, `ilan_genel`.`ozellik`, `ilan_genel`.`fiyat`, `ilan_genel`.`parabirimi`, `ilan_genel`.`kullanici`, `ilanresimler`.`resimlink` as resim, `uyeler`.`isim` as isim, `uyeler`.`soyisim` as soyisim, `kgsim_ilceler`.`isim` as ilce
FROM (`sanaltur`)
LEFT JOIN `ilan_genel` ON `ilan_genel`.`id` = `sanaltur`.`id`
LEFT JOIN `kgsim_ilceler` ON `kgsim_ilceler`.`id` = `ilan_genel`.`ilce`
LEFT JOIN `ilanresimler` ON `ilanresimler`.`id` = `ilan_genel`.`resim`
LEFT JOIN `uyeler` ON `uyeler`.`id` = `ilan_genel`.`kullanici`
ORDER BY `siralama` desc
LIMIT 30

回答1:

These are actually three very different queries. I don't think you will be able to usefully combine them. Also, they seem pretty fast to me.

However, if you want to try to optimize each individual query, you can use EXPLAIN SELECT to find out how if each query uses appropriate indexes or not.

For example:

EXPLAIN SELECT * 
FROM A 
WHERE foo NOT IN (1,4,5,6);

Might yield:

+----+-------------+-------+------+---------------
| id | select_type | table | type | possible_keys 
+----+-------------+-------+------+---------------
|  1 | SIMPLE      | A     | ALL  | NULL          
+----+-------------+-------+------+---------------

+------+---------+------+------+-------------+
| key  | key_len | ref  | rows | Extra       |
+------+---------+------+------+-------------+
| NULL | NULL    | NULL |    2 | Using where |
+------+---------+------+------+-------------+

In this case, the query had no possible_keys and therefore used no (or NULL) key to do the query. It's the key column you'd be interested in.

More information here:

http://dev.mysql.com/doc/refman/5.5/en/explain.html
http://dev.mysql.com/doc/refman/5.5/en/optimization-indexes.html

来源：https://stackoverflow.com/questions/8180902/is-there-better-way-to-do-these-mysql-queries

标签

mysql

join

subquery