????read uncommitted????????????

begin tran
set deadlock_priority low
update Earth set Animal='???'
waitfor  delay '0:0:5' --???5?????????????
rollback tran
??????????????????????????????
set tran isolation level read uncommitted
select * from Earth  --?????????????????????? ?????
waitfor  delay '0:0:5'  --5???????????????
select * from Earth  --???????????

????read committed????????????
????begin tran
????update Earth set Animal='???'
????waitfor  delay '0:0:10' --???5?????????????
????rollback tran
????set tran isolation level read committed
????select * from Earth ---???????????????????
????update Earth set Animal='????1'   --???????
????waitfor  delay '0:0:10'  --10????????????????????
????select * from Earth  --?????????????????????
??????μ?????????????о???????????ɡ?
????????????????
?????????????????????????????????????????????????????????????????????????????????????
?????????????????????????????????????????????????????????????????????????????????????????????????1222????
??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????в???1222?????ó???????????????????????????
????--????????????-1
????select @@lock_timeout
????--???ó?????
????set lock_timeout 0 --?0?????????????????????????????????????????????????????????????????????°?????hold??????
???????????????????????????????лл??over??