Question

我在mysql中有这个查询：

SELECT DISTINCT phone.phone AS phone
FROM phone 
 INNER JOIN person ON person.id = phone.person_id
 INNER JOIN locality  ON locality.id = person.locality_id
 INNER JOIN city ON city.id = locality.city_id
 INNER JOIN department ON department.id = city.department_id
 ORDER BY phone.id
LIMIT 10

EXPLAIN

TYPE      TABLE     TYPE    POSIBLE_KEYS                                 KEY               LEN     REF         ROWS     Extra
SIMPLE  department  index   PRIMARY                                       PRIMARY           4                   19      Using index; Using temporary; Using filesort
SIMPLE  city        ref     PRIMARY,fk_city_department                 fk_city_department   4   department.id   6       Using index
SIMPLE  locality    ref     PRIMARY,fk_locality_city                    fk_locality_city    4   city.id         1       Using index
SIMPLE  person      ref     PRIMARY,fk_person_locality                 fk_person_locality   5   locality.id     1596    Using index
SIMPLE  phone       ref     idx_phone,idx_phone_person,fk_phone_person  fk_phone_person     9   person.id       1

表格电话有900000行，表人有70万行，表格部门，城市和地区各有250行。

＆＃34; ORDER BY phone.id＆＃34;的执行时间。是20.125秒，没有＆＃34; ORDER BY phone.id＆＃34;是0.001秒。

我需要ORDER BY，如何优化查询？

非常感谢...

Answer 1

按字段排序是否有单独的索引？如果不是，则添加

Answer 2

我找到了解决方案。它在0.300秒内完成50000行。

     SELECT * FROM (SELECT phone.phone, phone.id AS pid FROM phone
        INNER JOIN person ON person.id = phone.person_id
        INNER JOIN locality ON locality.id = person.locality_id
        INNER JOIN city ON city.id = locality.city_id
        INNER JOIN department ON department.id = city.department_id 
        LIMIT 50000) AS tableaux
         ORDER BY tableaux.pid

如何在mysql中优化ORDER BY？

2 个答案: