CE computer MC about database management

1) 當 data 重複個陣就會浪費儲存空間，因為儲存兩隻完全一樣既 data items 係無意思的。

2) 當 data items 獨立於 program，你就可以用不同的 program 去使用呢d data items。舉個例，我有一堆會考考生資料既 data items，就可以有一個 print 成績單既program, 一個編排你考試試場地點既 program。如果唔獨立既話，每一個program 都要跟一 set data items。

3) 如果 d data items 只可以俾一個user 用，咁我有好多個 users 要用呢d data items 個陣咪要抄好多套 data items 分派俾 d users囉，這樣會很費時，因為 users 其實係需要同一set 既 data。

2) ALL Data items can use by any program. i.e. the database system have a connector to let any program connect to the database not only one specialized program. because your data may keep many years but you may be change the program platform. So, if the database specialized for one program. You are difficult to migrate your data to the other program.

3. That means the database can allow many concurrent connection. You can think-> if the data only can access by one user, then the other user need the first user competed transcation before the next database query.