【mysql】优化慢sql

SELECT
	space_id,
	max_temp,
	min_temp,
	avg_temp,
	create_time 
FROM
	( SELECT space_id, max_temp, min_temp, avg_temp, create_time FROM t_data_history ORDER BY create_time DESC LIMIT 99999 ) a 
GROUP BY
	a.space_id

SELECT
	a.*,
	b.max_temp,
	b.min_temp,
	b.avg_temp,
	b.x,
	b.y,
	b.z,
	b.circle_point,
	b.temperature 
FROM
	( SELECT max( create_time ) AS create_time, space_id FROM t_data_history a GROUP BY space_id ) a
	LEFT JOIN t_data_history b ON a.space_id = b.space_id 
	AND a.create_time = b.create_time

show variables like 'innodb_buffer_pool%';

SET GLOBAL innodb_buffer_pool_size = 3221225472

C:\ProgramData\MySQL\MySQL Server 5.7\my.ini