一條sql批量更新數據，update結合select 和 case when then

update employee_test b 
JOIN
(select empid,page,index_num,page * index_num  as  tindex from employee_test  where (page - 1) * 600 + index_num <n order by page desc)a
on a.empid = b.empid
set b.page =( case b.page when b.index_num + 1 > 600 then b. page + 1 else b.page end ),
b.index_num=(case b.index_num when b. index_num + 1 > 600 then b.index_num + 1 - b.page * 600  else b.index_num + 1 end)