17. SQL的例子Update employee set location=‘Beijing’ where id = ‘1234’创造一个新数据表
查询
投影数据
更新Create table employee {
name char[20] not null;
id char[12] not null;
dept char[20];
location char[10];
…
}Select name, id, dept from employee where name = ‘John’Select name, location from employee
29. Copyrighted (c) 1997, by Junsheng Long*不可靠网络上的可靠传输Missing packet
acknowledge and timeout
retransmission
Duplicate messages
sequencing packets
Out of order messages
sequencing packets
Flow control
wait and stop
window-sliding
Synchronization
hand shaking