ต้องการลบข้อมูล field ที่เหมือนกันในหลายๆ table ควรใช้ คำสั่ง Query แบบไหนดีครับ

ีupdate  table1, table2, table3, table4
set table1.field1='', table2.field2='', table3.field3='' table4.field4=''
where table1.bla=table2.bla and table1.bla=table3.bla and table1.bla=table4.bla

delete table1, table2, table3, table4
from table1, table2, table3, table4
where table1.bla=table2.bla and table1.bla=table3.bla and table1.bla=table4.bla

alter table tablename drop fieldname

delete  Sys_user, Sys_item, Sys_email, Sys_store,Sys_main
where User=1000

delete table1, table2, table3, table4
from table1, table2, table3, table4
where table1.User=table2.User 
and table1.User=table3.User 
and table1.User=table4.User
and table1.user=1000

delete Sys_Users_Detail,Sys_VIP_Info, Sys_Users_Texp, Sys_Users_Card, Sys_Users_Fight, DailyLogList, Sys_User_Gemstone, Sys_Users_Goods
from Sys_Users_Detail, Sys_VIP_Info, Sys_Users_Texp, Sys_Users_Card, Sys_Users_Fight, DailyLogList, Sys_User_Gemstone, Sys_Users_Goods
where Sys_Users_Detail.UserID = Sys_VIP_Info.UserID and Sys_Users_Detail.UserID = Sys_Users_Texp.UserID  and Sys_Users_Detail.UserID = Sys_Users_Card.UserID and Sys_Users_Detail.UserID = Sys_Users_Fight.UserID and Sys_Users_Detail.UserID = DailyLogList.UserID and Sys_Users_Detail.UserID = Sys_User_Gemstone.UserID and Sys_Users_Detail.UserID = Sys_Users_Goods.UserID and Sys_Users_Detail.UserID = 1