優化MySQL連接查詢以刪除使用臨時並使用索引？

Question

我有一個查詢ORDER BY name和name索引被忽略。

如何優化查詢以使用索引並擺脫EXPLAIN中的Using temporary？

我有log-queries-not-using-indexes啓用，我看到這個查詢成千上萬次。

這裏的查詢：

SELECT l.parent_id, j.id, j.location_id, j.currency, j.frequency, ROUND((j.salary_min + j.salary_max)/2) as salary 
FROM jobs AS j 
JOIN location AS l 
    ON j.location_id = l.id 
WHERE j.salary_min !=0 
    AND j.status != 'Rejected'  
    AND l.published =1 
    AND date_sub(now(), interval 1 month) <= j.effected_date 
ORDER BY l.name 

的解釋：

+----+-------------+-------+--------+----------------------------------+---------------+---------+----------------------------+------+----------------------------------------------+ 
| id | select_type | table | type | possible_keys     | key   | key_len | ref      | rows | Extra          | 
+----+-------------+-------+--------+----------------------------------+---------------+---------+----------------------------+------+----------------------------------------------+ 
| 1 | SIMPLE  | j  | range | effected_date,location_id,status | effected_date | 9  | NULL      | 562 | Using where; Using temporary; Using filesort | 
| 1 | SIMPLE  | l  | eq_ref | PRIMARY       | PRIMARY  | 4  | esljw_joomla.j.location_id | 1 | Using where         | 
+----+-------------+-------+--------+----------------------------------+---------------+---------+----------------------------+------+----------------------------------------------+ 
2 rows in set (0.01 sec) 

而且表結構：

CREATE TABLE IF NOT EXISTS `jobs` (
    `id` int(11) NOT NULL AUTO_INCREMENT, 
    `location_id` varchar(255) NOT NULL, 
    `status` varchar(255) DEFAULT NULL, 
    `currency` varchar(255) DEFAULT NULL, 
    `salary_min` int(11) DEFAULT NULL, 
    `salary_max` int(11) DEFAULT NULL, 
    `effected_date` datetime DEFAULT NULL, 
    `frequency` varchar(255) NOT NULL DEFAULT '1', 
    PRIMARY KEY (`id`), 
    KEY `effected_date` (`effected_date`), 
    KEY `location_id` (`location_id`), 
    KEY `status` (`status`) 
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=10130 ; 

CREATE TABLE IF NOT EXISTS `location` (
    `id` int(11) NOT NULL AUTO_INCREMENT, 
    `name` varchar(128) DEFAULT NULL, 
    `parent_id` int(11) DEFAULT NULL, 
    PRIMARY KEY (`id`), 
    KEY `name` (`name`) 
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=304 ; 

Answer 1

1. 添加published + id綜合指數location表
2. 移動l.published =1條件的ON條款

這是什麼，你可以在你的情況下做的。但是，由於您不是通過主表進行排序，而是通過聯接表進行排序，因此，您將永遠無法擺脫using temporary。

Answer 2

這是因爲您首先列出了job。更改表格的順序，如下所示：

SELECT l.parent_id, j.id, j.location_id, j.currency, j.frequency, ROUND((j.salary_min + j.salary_max)/2) as salary 
FROM location AS l 
JOIN jobs AS j ON j.location_id = l.id 
WHERE j.salary_min !=0 
AND j.status != 'Rejected'  
AND l.published =1 
AND date_sub(now(), interval 1 month) <= j.effected_date 
ORDER BY l.name 

試試看，併發布它如何去。

Answer 3

很多時候我已經做了查詢，在查詢中有適當的主表作爲第一個查詢，並且具有良好的索引，單獨添加STRAIGHT_JOIN可以修復查詢。因此，與現有的標準，你應該是好您的日期索引和使用，作爲主要標準......如

SELECT STRAIGHT_JOIN 
     L.Parent_ID, 
     J.id, 
     J.location_id, 
     J.currency, 
     J.frequency, 
     ROUND((J.salary_min + J.salary_max)/2) as Salary 
    FROM 
     jobs J 
     join Location L 
      on J.Location_ID = L.ID 
      AND L.Published = 1 
    WHERE 
      J.Effected_Date >= date_sub(now(), interval 1 month) 
     AND J.salary_min != 0 
     AND J.status != 'Rejected' 
    ORDER BY 
     L.name