Database Basics
The purpose of a database is to store the day-to-day operational information required by an organization. Any means of collecting and organizing data is a database.
數據庫基礎
數據庫用來儲存辦公機構的日常操作信息。任何數據存儲和組織機制都可稱之為數據庫。
Prior to theInformation Age, information was primarily stored on cards, in file folders, or in ledger books. Before the adding machine, offices employed dozens of workers who spent all day adding columns of numbers and double-checking the math of others. The title of those who had that exciting career was computer.
在信息時代到來之前，信息數據通常被存儲在卡片、文件夾、或紙質書刊中。在相關機器被推廣使用之前，機構部門雇傭大量職員終日進行添加數據、檢查數學運算結果正確性等繁重而重復的工作。這類職員所從事的工作在當時被稱作“人力計算機（computer）”
As the number crunching began to be handled by digital machines, human labor, rather than being eliminated, shifted to other tasks. Analysts, programmers, managers, and IT staff have replaced the human “computers” of days gone by.
隨著數字設備越來越多的被應用到數據處理工作當中，“人力計算機”們並沒有失業，而是轉入了其他相關工作。 進而“人力計算機”這壹工作逐漸消失而被諸如數據分析師，程序員，管理人員，和IT員工所取代。
Benefits of a Digital Database
數字數據庫的好處
The Information Age and the relational database brought several measurable benefits to organizations:
信息時代和關系數據庫給現代辦公機構帶來極大好處
Increased data consistency and better enforcement of business rules數據壹致性和商業邏輯性得到增強
Improved sharing of data, especially across distances數據***享， 尤其是遠程數據***享變得極為便利。
Faster searches for and retrieval of data可以更快的對數據進行檢索和獲取
Improved generation of comprehensive reports強大的數據報表生成功能。
Improved ability to analyze data trends強大數據趨勢分析能力。
The general theme is that a computer database originally didn’t save time in the entry of data, but rather in the retrieval of data and in the quality of the data retrieved. However, with automated data collection in manufacturing, bar codes in retailing, databases sharing more data, and consumers placing their own orders on the Internet, the effort required to enter the data has also decreased.
通常認為計算機數據庫只增強了數據檢索功能以及檢索結果的質量，在數據錄入方面和傳統方法相比效率並無明顯提高。然而，隨著制造業數據采集自動化程度的加強、零售業條形碼的普及、計算機數據庫***享更多數據、多數顧客開始習慣網上購物， 所有這些因素使得數據錄入的效率也得到了極大的提升。
Tables, Rows, Columns
A relational database collects common, or related, data in a single list. For example, all the product information may be listed in one table and all the customers in another table. A table appears similar to a spreadsheet and is constructed of columns and rows. The appeal
of the spreadsheet is its informal development style, which makes it easy to modify and add to as the design matures. In fact, managers tend to store critical information in spreadsheets, and many databases started as informal spreadsheets.In both a spreadsheet and a database table, each row is an item in the list and each column is
a specific piece of data concerning that item. So each cell should contain a single piece of data about a single item. While a spreadsheet tends to be free-flowing and loose in its design,
database tables should be very consistent as to the meaning of the data in a column. Because row and column consistency is so important to a database table, the design of the table is critical.
表，行，列
關系數據庫將同類或相關數據組織在壹起, 例如，所有產品的信息可以存入壹個表， 所有顧客信息可以存入另壹個表。數據庫中的表看起來像是壹個電子表格，它由行和列組成。電子表格最大的優勢在於它的結構靈活，可以自由的修改
或定型為成品。事實上，管理人員傾向於把重要信息存入表格，多數數據庫系統就是根據這種需要從電子表格基礎上應運而生。
無論在電子表格或是數據庫表中，每壹行都是表中的壹個條目，而每壹列則是組成這個條目的壹個特定的數據片。 而電子表格和數據庫表的最大不同在於，電子表格結構變換不定，設計松散，而數據庫表設計中，行列數據的壹致性非常重要，需要嚴格保證表中數據和數據列的定義之間存在邏輯正確性。因此，數據庫表的設計至關重要。
Over the years different development styles have referred to these columns with various
different terms, listed in Table 2-1.
近年來出現過很多數據庫設計方法， 見下表2-1