如何有效地创建索引

Question

I wish to know how I can create indexes in my database according to my data structure. most of my queries are fetching data against the ID and the name as well with two or three tables joining while pagination. please advise how to make indexes according to below queries.

Query:1

SELECT DISTINCT topic, type FROM books where type like 'Tutor-Books' order by topic

Explain:

id  select_type table   type    possible_keys   key key_len ref rows    Extra   
1   SIMPLE  books   range   faith   faith   102 NULL    132 Using index condition; Using temporary; Using filesort

Query:2

SELECT  books.name, books.name2, books.id, books.image, books.faith,
        books.topic, books.downloaded, books.viewed, books.language,
        books.size, books.author as author_id, authors.name as author_name,
        authors.aid
    from  books
    LEFT JOIN  authors ON books.author = authors.aid
    WHERE  books.id = '".$id."'
      AND  status = 1 

Explain:

id  select_type table   type    possible_keys   key key_len ref rows    Extra   
1   SIMPLE  books   const   PRIMARY PRIMARY 4   const   1   NULL
1   SIMPLE  authors const   aid aid 4   const   1   NULL

Can i use indexes for pagination in offset case where same query returns total:

SELECT  SQL_CALC_FOUND_ROWS books.name, books.name2, books.id,
        books.image, books.topic, books.author as author_id,
        authors.name as author_name, authors.aid
    from  books
    LEFT JOIN  authors ON books.author = authors.aid
    WHERE  books.author = '$pid'
      AND  status = 1
    ORDER BY  books.name
    LIMIT  $limit OFFSET $offset 

Do I need to update my queries after creating indexes. please also suggest what should be the table format.

SHOW CREATE TABLE books:

Table   Create Table    
books   CREATE TABLE `books` (
 `name` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
 `name2` varchar(150) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
 `author` int(100) NOT NULL,
 `translator` int(120) NOT NULL,
 `publisher` int(100) NOT NULL,
 `pages` int(50) NOT NULL,
 `date` varchar(50) CHARACTER SET latin1 NOT NULL,
 `downloaded` int(100) NOT NULL,
 `alt_lnk` text NOT NULL,
 `viewed` int(100) NOT NULL,
 `language` varchar(100) CHARACTER SET latin1 NOT NULL,
 `image` varchar(200) CHARACTER SET latin1 NOT NULL,
 `faith` varchar(100) CHARACTER SET latin1 NOT NULL,
 `id` int(100) NOT NULL AUTO_INCREMENT,
 `sid` varchar(1200) CHARACTER SET latin1 DEFAULT NULL,
 `topic` varchar(100) CHARACTER SET latin1 NOT NULL,
 `last_viewed` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
 `size` double NOT NULL,
 `status` int(2) NOT NULL DEFAULT '0',
 `is_scroll` int(2) NOT NULL,
 `is_downloaded` int(2) NOT NULL,
 `pdf_not_found` int(2) NOT NULL,
 PRIMARY KEY (`id`),
 KEY `name` (`name`),
 KEY `downloaded` (`downloaded`),
 KEY `name2` (`name2`),
 KEY `topic` (`topic`),
 KEY `faith` (`faith`)
) ENGINE=InnoDB AUTO_INCREMENT=12962 DEFAULT CHARSET=utf8

Answer 1

where type like 'Tutor-Books' order by topic  (or:)
where type   =  'Tutor-Books' order by topic
--> INDEX(type, topic)

where type like '%Tutor-Books' order by topic
--> INDEX(topic) -- the leading % prevents indexing

LEFT JOIN  authors ON books.author = authors.aid
--> PRIMARY KEY(aid)

Do you really need LEFT JOIN ? If you can change it to JOIN , the optimizer might be able to start with authors . If it does, then

--> INDEX(author) -- in `books`

My cookbook for building indexes.

Other tips:

• INT(100) and INT(2) are identical -- each is a 4-byte signed integer. Read about TINYINT UNSIGNED for numbers 0..255, etc. Use that for your flags (status, is_scroll, etc)
• DATE is a datatype; using a VARCHAR is problematic if you ever want to compare or order.
• Learn about composite indexes, such as my first example.

Answer 2

Your display widths are a little funky, but that wont cause a problem.

Query 1:

• You're using the LIKE operator without a wildcard search % . You can likely swap this with an = operator.
• I don't see the column type in your SHOW CREATE TABLE -- but it seems you don't have an index here, unless you renamed it to faith .
• Do you need to type to be a string? could it be abstracted to a types table and then joined against using an integer? Or, if you have a fixed amount of types that's unlikely to change, could you use an enum ?

Query 2:

• You don't need to quote strings, also that's probably vulnerable to SQL injection. do ='.intval($id).' instead.
• Make sure you have an index on authors.aid and that they're of the same type.