mysql的update更新根据查询语句的内容

update project pp set extdatefield3=(select a.finisheddate from (select p.id,w.finisheddate from project p INNER JOIN pw_proposal pw on pw.projectid=p.id INNER JOIN workflowbase w on w.id=pw.requestid where w.isdelete=0 and w.isfinished=1 and p.isdelete=0 and p.projectphase='40288148117d0ddc01117d77f7290d3e' ) a where a.id=pp.id)
where (extdatefield3 is null or extdatefield3='')