3334
資料庫 問題!!!
CODE .........MANAGER ......... PHONE ...........ADDRESS .......... PRICE21-5Z ...........HOLLY ................3384567 .............3334..................16825-2D ...........JANE .................1234567 ............. 218...................12525-5A ...........GEORGE ..............7654321 .............124...................32525-9T ............HOLLY ................ 3384567............3334.................. 21527-4Q ............GEORGE................ 7654321............124................... 10329-2D.............HOLLY ................ 3384567 ..............3334 .............. 25531-7P ............WILLAM ............... 4455667 .............216................ 568上面是個表格!! 說明: 人名省略姓氏 電話隨便打的 地址只打開頭區碼 !!!!1.How many records does the file contain and how many fields are there per record?2.What problem would you encounter if you wanted to produce a listing by city?How would you solve this problem by altering the file structure?3.If you wanted to produce a listing of the file contents by last name area code city state or zip code how would you alter the file structure?4.What data redundancies do you detect and how could those redundancies lead to anomalies?
(1)在資料庫中
除了最上列之欄位名稱以外
一列橫向的完整資料稱作一個record
依你的題目則有7個而每一個直欄就稱作field
所有共有5個(2)你的表中並沒有城市的欄位名稱
所以如果要以城市為依據製作報表
則必須在資料表檔案中
加入一個稱為城市(city)欄位(可以從address欄位中分割出來)
才可以達到目的(3)如果想要利用zip-code 或code-city-state來產生報表
那麼必須把address的欄位內容切割成郵遞區號(zip-code)和村鎮地址(town-address)兩欄
整個資料表欄位變成(CODE
MANAGER
PHONE
ZIPCODE
TOWNADDR
PRICE)
那麼就可以很容易用來區分出不同的城市屬性資料.(4)這個表中MANAGER
PHONE
ADDRESS三個欄位因資料內容彼此有一致性關係且重複性相當高
造成許多資料是多餘的
因此可將原來的MANAGER
PHONE
ADDRESS用一個獨立的資料表檔案來將重複性資料減少
建立如下表ID............MANAGER ......... PHONE ...........ADDRESS1...............HOLLY ................3384567 .............33342................JANE ...................1234567 .............. 2183..............GEORGE .............7654321 ................1244...............WILLAM ............ 4455667 ...............216那麼只需將原來資料表欄位改為(CODE
ID
PRICE)三個欄位
如下表CODE .........ID .........PRICE21-5Z ............1.............16825-2D ...........2 .............12525-5A ...........3 .............32525-9T ............1 ............ 21527-4Q ............3.............10329-2D.............1 ........... 25531-7P ............4 ............568並且用ID來連結關聯一樣可以得到想要的資料 參考資料 資料庫的書