mysql添加索引和不添加索引的区别及说明

目录

• mysql添加索引和不添加索引区别
• 定位到该sql语句后发现是一个非常简单的select查询
• 查询目前表数据条数
• 通过使用explain 定位看到
• 在使用explain查看select执行情况
• 总结

SELECT
    t.id,
    t.job_group,
    t.job_id,
    t.executor_address,
    t.executor_handler,
    t.executor_param,
    t.executor_sharding_param,
    t.executor_fail_retry_count,
    t.trigger_time,
    t.trigger_code,
    t.trigger_msg,
    t.handle_time,
    t.handle_code,
    t.handle_msg,
    t.alarm_status
FROM
    xxl_job_log AS t
WHERE
t.trigger_time >= '2020-01-01 00:00:00.0'
AND 
t.trigger_time <= '2020-01-01 23:59:59.0'
 AND
alarm_status = 0
ORDER BY
t.trigger_time DESC
LIMIT 0,
 10

t.trigger_time >= '2020-01-01 00:00:00.0'
AND 
t.trigger_time <= '2020-01-01 23:59:59.0'

ORDER BY
t.trigger_time DESC

ALTER TABLE xxl_job_log ADD INDEX index_job_time (trigger_time)