This is part two of the question: MySql: make this query faster... is there a way?
this query still run slowly:
SELECT b.id,
b.name,
c.name
FROM bookcorr as a JOIN books as b on b.id = a.books_id =
JOIN Library as c on c.id = a.library_id
WHERE a.category_id = '2521'
AND a.library_id = '4983'
ORDER BY b.name ASC LIMIT 0,15
Any suggest ?
CREATE TABLE `bookcorr` (
`category_id` smallint(4) unsigned NOT NULL,
`book_id` mediumint(7) unsigned NOT NULL,
`library_id` smallint(5) unsigned NOT NULL,
UNIQUE KEY `cat_id_3` (`category_id`,`book_id`,`library_id`),
KEY `category_id` (`category_id`),
KEY `book_id` (`book_id`),
KEY `library_id` (`library_id`),
KEY `cat_id_2` (`cat_id`,`com_id`))
CREATE TABLE `books` (
`id` mediumint(7) unsigned NOT NULL AUTO_INCREMENT,
`com_id` smallint(5) unsigned NOT NULL,
`name` varchar(256) NOT NULL,
....
PRIMARY KEY (`id`),
KEY `name` (`name`),
FULLTEXT KEY `search` (`name`,`author`)
)
CREATE TABLE `Library` (
`id` smallint(4) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(256) NOT NULL,
...
UNIQUE KEY `id` (`id`),
KEY `library_name` (`name`)
)
CREATE TABLE `Category` (
`id` smallint(4) unsigned NOT NULL,
`name` varchar(100) NOT NULL,
UNIQUE KEY `id` (`id`),
KEY `name` (`name`),
)
Here:
+----+-------------+-------+--------+----------------------------------------+----------+---------+----------------------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+----------------------------------------+----------+---------+----------------------------+------+-------------+
| 1 | SIMPLE | b | index | NULL | name | 258 | NULL | 15 | |
| 1 | SIMPLE | a | eq_ref | cat_id_3,cat_id,book_id,library_id | cat_id_3 | 7 | const,b.id,const | 1 | Using index |
| 1 | SIMPLE | c | const | PRIMARY | PRIMARY | 2 | const | 1 | Using where |
+----+-------------+-------+--------+----------------------------------------+----------+---------+----------------------------+------+-------------+
Looks like you need to study how to use "explain select".
It will make all your queries faster! :)
SELECT b.id,
b.name,
c.name
FROM books as b
JOIN bookcorr as a
ON a.books_id = b.id
AND a.category_id = '2521'
AND a.library_id = '4983'
JOIN Library as c
ON c.id = a.library_id
ORDER BY
b.name ASC
LIMIT 15
Create the following indexes:
books (name)
bookcorr (category_id, library_id, books_id)
Update:
If you need the total record count, it would be better doing it in two queries.
Assuming that books_id
and library_id
always reference a record in books
and library
, use this query:
SELECT COUNT(*)
FROM bookcorr a
WHERE a.category_id = '2521'
AND a.library_id = '4983'
to calculate the count.
Update 2:
SELECT b.id,
b.name,
c.name
FROM books b USE INDEX (name)
STRAIGHT_JOIN
bookcorr a
ON a.books_id = b.id
AND a.category_id = '2521'
AND a.library_id = '4983'
STRAIGHT_JOIN
Library as c
ON c.id = a.library_id
ORDER BY
b.name ASC
LIMIT 15
在bookcorr表中添加一个books_id索引。如果查询仍然很慢,请尝试使用数字id作为books(整数)。
mysql> explain SELECT b.id,b.name,c.name FROM bookcorr as a JOIN books as b on a.book_id = b.id JOIN library as c on b.library_id=c.id WHERE a.category_id = '2302' AND a.library_id = '4983' order by b.name asc LIMIT 0,15;
+----+-------------+-------+--------+----------------------------------------+----------+---------+--------------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+----------------------------------------+----------+---------+--------------------+------+----------------------------------------------+
| 1 | SIMPLE | a | ref | cat_id_3,cat_id,book_id,library_id | cat_id_3 | 4 | const,const | 1788 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | b | eq_ref | PRIMARY,library_id | PRIMARY | 3 | dbname.a.book_id | 1 | |
| 1 | SIMPLE | c | eq_ref | PRIMARY | PRIMARY | 2 | dbname.b.library_id| 1 | |
+----+-------------+-------+--------+----------------------------------------+----------+---------+--------------------+------+----------------------------------------------+
是错字还是为什么在原始查询中这样的SQL(?):
JOIN books as b on b.id = a.books_id = JOIN Library as c on c.id = a.library_id
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