database definition computer

primary key to either party can 1:n : For example UserInfo and cardinfo are on the registration side is 1:n the Relationship UserInfo(userid,password,username,userlevel) Cardinfo(cardno,balance,cardstate) After conversion Cardinfo(cardno,userid,balance,cardstate) The primary key is placed on the n - side N:m : For example UserInfo and cardinfo are in the recharge aspect is n:m Relationship ( One user can recharge multiple cards, one card can be recharged by multiple users ) Cardinfo(cardno,b

Label:The first kind: Can ping pass, show you in the same network, can directly access. You just have to add external access to the account in your logged in user ... That is, authorization. For example, your account is root and you can enter MySQL afterYou can see that each account has a column of host, this is the host to allow login, if the host is the% number, then all hosts can log on, including the remote host. I do the followingThen one of my root accounts can be accessed by all hosts.In