Question

I have problem with SQL query, is any way how to speed up this query?
Table word contains 14 000 rows a query took 4.5631 sec on localhost.

    SELECT 
    (SELECT SUM((SELECT COUNT(*)
                    FROM word w
                    WHERE w.lecture_id = l._id AND active = 1))
        FROM lecture l
        WHERE l.book_id = b._id) AS active_word_count,
    (SELECT SUM((SELECT COUNT(*)
                 FROM word w
                 WHERE w.lecture_id = l._id))
        FROM lecture l
        WHERE book_id = b._id) AS word_count,
    (SELECT COUNT(*)
     FROM lecture l
     WHERE l.book_id = b._id) AS lecture_count,
    b._id,
    b.name,
    b.version
FROM book b



CREATE TABLE book (
  _id int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  version tinyint(3) unsigned NOT NULL,
  lang tinyint(4) NOT NULL DEFAULT '1',
  PRIMARY KEY (_id)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=21 ;

CREATE TABLE lecture (
  _id int(11) NOT NULL AUTO_INCREMENT,
  book_id int(11) NOT NULL,
  lecture_name varchar(255) NOT NULL,
  PRIMARY KEY (_id)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=155 ;

CREATE TABLE word (
  _id int(11) NOT NULL AUTO_INCREMENT,
  question varchar(255) NOT NULL,
  answer varchar(255) NOT NULL,
  active tinyint(1) NOT NULL,
  lecture_id int(11) NOT NULL,
  PRIMARY KEY (_id)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

Query returns data, witch are available here: http://pastebin.com/80KNsU7Y

Thank you for help.

Answer 1

I added some JOINs. So it should be faster now. http://sqlfiddle.com/#!2/eec80/15

SELECT
    (SELECT COUNT(*)
        FROM word w
        JOIN lecture l ON l._id = w.lecture_id
        WHERE l.book_id = b._id
        AND w.active = 1) AS active_word_count,
    (SELECT COUNT(*)
        FROM word w
        JOIN lecture l ON  w.lecture_id = l._id
        WHERE l.book_id = b._id) AS word_count,
    (SELECT COUNT(*)
        FROM lecture l
        WHERE l.book_id = b._id) AS lecture_count,
    b._id,
    b.name,
    b.version
FROM book b