有两张表 workflow(工单表）workflowhistory(工单流转历史表） id号唯一 ，每条工单的flownumber 从1开始递增。
table workflow
id name
00 content
01 content
table workflowhistory
id flownumber dealtime
00 1 2007-10-9 20:00:00
00 2 2007-10-10 20:00:00
01 1 2007-10-9 20:00:00
01 2 2007-10-10 20:00:00
求sql语句 把workflow workflowhistory 通过id连接起来，并且每个id只保留时间最晚的记录（或者说是flownuber最大的那条记录）
ru
id flownumber dealtime
00 2 2007-10-10 20:00:00
01 2 2007-10-10 20:00:00
------解决方案--------------------------------------------------------
select * from (select * from workflowhistory
where flownumber in (select max(flownumber) from workflowhistory group by id)) a join workflow on workflow.id= a.id