SELECT
	ReqColumns, hostid, name, (TotalUsed/TotalMemory)* 100 AS Value
FROM
	(
		SELECT
			sc.ReqColumns, i.hostid, i.name, 
			/*TRUNCATE((tu.value_min) / (1024 * 1024 * 1024), 2) AS value_min, 
			TRUNCATE((tu.value_avg) / (1024 * 1024 * 1024), 2) AS value_avg,
			TRUNCATE((tu.value_max) / (1024 * 1024 * 1024), 2) AS value_max,*/
			SUM(IF(i.name='Total Memory [used]',TRUNCATE((tu.value_max) / (1024 * 1024 * 1024), 2) ,0)) AS TotalUsed,
			SUM(IF(i.name='Total Memory',TRUNCATE((tu.value_max) / (1024 * 1024 * 1024), 2) ,0)) AS TotalMemory
			 
		FROM
			trends_uint tu
			INNER JOIN items i
				ON   i.itemid = tu.itemid
			INNER JOIN graphs_items gi
				ON   gi.itemid = i.itemid
			INNER JOIN graphs g
				ON   g.graphid = gi.graphid
			INNER JOIN HOSTS h
				ON   h.hostid = i.hostid
                        LEFT JOIN flip_linkutilisation.servercolumns sc 
                                ON   sc.ColumnDetails = g.name
		WHERE
			i.name IN ('Total Memory', 'Total Memory [Free]', 
			              	        'Total Memory [used]')
		GROUP BY sc.ReqColumns, i.hostid, i.name
	) AS x

well我想这会解决你的问题吗？



注意我删除不必要的连接和列并减少读取次数

well i think this will solve your problem?

watch out i remove the unnecessary joins and columns and reduce the number of reads