MySQL Left join take too long for huge data - mysql

Question

I have two tables .Property tables and it related photo.One property may have many photo but I want only one any of it related photo, When I use left join MySQL query it become too slow.
Here is my query
SELECT `sp_property`.`id` as propertyid, `sp_property`.`property_name`, `sp_property`.`property_price`, `sp_property`.`adv_type`, `sp_property`.`usd`, `images`.`filepath_name`
FROM (`sp_property`)
LEFT JOIN (select id, Max(property_id) as pid,filepath_name
from sp_property_images
group by property_id) `images`
ON `images`.`pid` = `sp_property`.`id`
WHERE `sp_property`.`published` = 'yes'
GROUP BY `propertyid`
ORDER BY `sp_property`.`feature_listing` desc, `submit_date` desc
LIMIT 1,20
CREATE TABLE IF NOT EXISTS `sp_property_images` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`property_id` varchar(100) NOT NULL,
`filepath_name` text,
`label_name` varchar(45) DEFAULT NULL,
`primary` char(10) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `property_id` (`property_id`),
KEY `id` (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=12941 ;
CREATE TABLE IF NOT EXISTS `sp_property` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`propertytype` varchar(50) NOT NULL,
`adv_type` varchar(45) NOT NULL,
`property_name` text,
`division` varchar(45) NOT NULL,
`township` varchar(45) NOT NULL,
`property_price` decimal(20,2) unsigned DEFAULT NULL,
`price_type` varchar(45) NOT NULL,
`availability` varchar(100) DEFAULT NULL,
`property_address` text,
`p_dimension_length` varchar(45) NOT NULL,
`p_dimension_width` varchar(45) NOT NULL,
`p_dimension_sqft` varchar(45) NOT NULL,
`p_dimension_acre` varchar(45) NOT NULL,
`floor` varchar(45) NOT NULL,
`phone` varchar(100) DEFAULT NULL,
`aircorn` varchar(45) NOT NULL,
`ownership` varchar(45) NOT NULL,
`bedroom` varchar(45) NOT NULL,
`bathroom` varchar(45) NOT NULL,
`special_feature` text,
`amentites` text,
`property_detail` text,
`submit_date` datetime DEFAULT NULL,
`published` varchar(45) NOT NULL,
`published_date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`agent_id` varchar(45) NOT NULL,
`source` varchar(45) NOT NULL,
`contact_name` varchar(100) NOT NULL,
`contact_no` varchar(100) NOT NULL,
`contact_address` text NOT NULL,
`contact_email` varchar(100) NOT NULL,
`unit_type` varchar(100) DEFAULT NULL,
`map_lat` varchar(100) DEFAULT NULL,
`map_long` varchar(100) DEFAULT NULL,
`show_map` varchar(3) DEFAULT 'no',
`total_view` bigint(20) NOT NULL DEFAULT '0',
`feature_listing` varchar(10) NOT NULL DEFAULT 'no',
`new_homes_id` int(11) NOT NULL,
`publish_price` int(1) NOT NULL DEFAULT '0',
`usd` decimal(20,2) NOT NULL,
`tag_id` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=18524 ;

Answer 1

Have you added indices on your tables? You would need three indices on the following columns:
article_photo.a_id for grouping and joining
article_photo.p_id for sorting
article.a_id for joining (although this is hopefully already the PK of your table)
The result of joins is not guaranteed to be sorted in any order, so you probably want to move your ORDER BY clause from the subquery to the outer query:
SELECT * from `article`
LEFT JOIN (
SELECT * from `article_photo`
GROUP BY `a_id`) as images
ON article.a_id = images.a_id
ORDER BY images.p_id DESC
Also, you have no guarantee on which article_photo you will get, since select data without an aggregate function (and only MySQL will allow you to do that).
Now that the question contains the real tables and all information essential to answering, here's my take – first, here's your query:
SELECT `sp_property`.`id` as propertyid, `sp_property`.`property_name`, `sp_property`.`property_price`, `sp_property`.`adv_type`, `sp_property`.`usd`, `images`.`filepath_name`
FROM (`sp_property`)
LEFT JOIN (select id, Max(property_id) as pid,filepath_name
from sp_property_images
group by property_id) `images`
ON `images`.`pid` = `sp_property`.`id`
WHERE `sp_property`.`published` = 'yes'
GROUP BY `propertyid`
ORDER BY `sp_property`.`feature_listing` desc, `submit_date` desc
LIMIT 1,20
Let's see. you are joining sp_property_images.property_id with sp_property.id. These columns have different types (int vs. varchar) and I suppose this results in a severe performance penalty (since the values have to be converted to the same type).
Then, you are filtering by sp_property.published, so I suggest adding an index on this column as well. Also, examine if you really need to have this column as varchar. A bool/bit flag probably suffices as well (if it doesn't, an enum might be a better choice still).
Ordering benefits from an index too. Add an index spanning both columns sp_property.feature_listing and sp_property.submit_date.
If all of the above still doesn't help, you might have to remove the sub-select. It might prevent the mysql engine from recognizing (and using!) the index you have defined on the sp_property_images.property_id column.

Answer 2

This simple query will give you what you asked for, all articles with their photos
SELECT ar.a_id, ar.a_title, ap.p_id, ap.photo_name
FROM article ar
JOIN article_photo ap on ar.a_id = ap.a_id
No reason for left join and grouping there or you wanna get sum on photos by article?