即使只查询一个内容,也需要2秒:select max(data.id) id, data.node_mac, node.name node_name, max(data.up_date) up_date, group_concat(data.temperature order by up_date desc separator ',') as temperature from t_data data left join t_node node on data.node_mac = node.mac inner join t_modulename modulename on modulename.module_name = node.name group by node_mac
贴出 explain select ... 显示一下执行计划以分析效率。
Creating Sort Index 3.9 s 65.60% 1 3.9 s sending data 1.9 s 34.00%
group_concat(data.temperature order by up_date desc separator ',') as temperature
from t_data data
left join t_node node on data.node_mac = node.mac
inner join t_modulename modulename on modulename.module_name = node.name
group by node_mac
Creating Sort Index 3.9 s 65.60% 1 3.9 s
sending data 1.9 s 34.00%