Question

我有这个问题：

select * from

当我执行它时，需要约45秒，记录为35k。每天我都会向gps_unit_location表添加5k +新记录。所以桌子会增长。我所有id的当前索引。是否会添加任何其他索引可以帮助我提高此查询的性能？

感谢。

Answer 1

所以，

请确保您拥有NOT NULL列和索引：

INDEX ON gps_unit_location.idgps_unit_location
INDEX ON user.iduser
INDEX ON user_to_gps_unit.iduser
INDEX ON user_to_gps_unit.idgps_unit
INDEX ON gps_unit.idgps_unit
INDEX ON gps_unit_location.idgps_unit

请确保您确实需要选择该明星所有字段*

尝试此查询：

SELECT 
    `gps_unit`.`idgps_unit`, 
    `gps_unit`.`name as name`, 
    `gps_unit`.`notes as notes`, 
    `gps_unit`.`serial`, 
    `gps_unit_location`.`dt` as dt, 
    `gps_unit_location`.`idgps_unit_location`,
    `gps_unit_location`.`lat`, 
    `gps_unit_location`.`long`,
    `ip`,
    `unique_id`,
    `loc_age`,
    `reason_code`,
    `speed_kmh`,
    `VehHdg`,
    `Odometer`,
    `event_time_gmt_unix`,
    `switches`,
    `engine_on_off`
FROM user 
INNER JOIN user_to_gps_unit  ON user.iduser = user_to_gps_unit.iduser 
INNER JOIN gps_unit          ON user_to_gps_unit.idgps_unit = gps_unit.idgps_unit
INNER JOIN gps_unit_location ON gps_unit.idgps_unit = gps_unit_location.idgps_unit
INNER JOIN
        (SELECT
             `gps_unit_location`.`idgps_unit`,
             MAX(`gps_unit_location`.`dt`) dtmax
         FROM `gps_unit_location`
         GROUP BY 1
         ) r1 ON r1.idgps_unit = gps_unit_location.idgps_unit AND r1.dtmax = gps_unit_location.dt
WHERE 
    user.iduser = 14

另外，我认为您不需要在定义为主键的列上使用唯一索引，这会导致插入/更新语句的写入开销。

Answer 2

通用答案是索引那些用于连接和约束的列（ON和WHERE子句）。使用复合索引（首先连接，然后是第一个具有最低基数约束的约束）。

哦，让你的所有身份证都'无符号'。

查询很慢，要索引哪些字段

2 个答案: