tailieunhanh - Hướng dẫn học Microsoft SQL Server 2008 part 9

Tôi có thể cảm nhận được nhịp điệu, nhưng tôi phải làm việc thông qua các hợp âm và con số chúng ra gần như toán học trước khi tôi có thể chơi bất cứ điều gì, nhưng một mảnh đơn giản. | Relational Database Design v . i . -i. .-i -. cSrl I play jazz guitar well I used to play before life became so busy. You can listen to some of my MP3s on my about page on . There are some musicians who can hear a song and then play it I m not one of those. I can feel the rhythm but I have to work through the chords and figure them out almost mathematically before I can play anything but a simple piece. To me building chords and chord progressions is like drawing geometric patterns on the guitar neck using the frets and strings. Music theory encompasses the scales chords and progressions used to make music. Every melody harmony rhythm and song draws from music theory. For some musicians there s just a feeling that the song sounds right. For those who make music their profession they understand the theory behind why a song feels right. Great musicians have both the feel and the theory in their music. Designing databases is similar to playing music. Databases are designed by combining the right patterns to correctly model a specific solution to a problem. Normalization is the theory that shapes the design. There s both the mathematic theory of relational algebra and the intuitive feel of an elegant database. Designing databases is both science and art. IN THIS CHAPTER Introducing entities tuples and attributes Conceptual diagramming vs. SQL DDL Avoiding normalization over-complexity Choosing the right database design pattern Ensuring data integrity Exploring alternative patterns Normal forms Database Basics The purpose of a database is to store the information required by an organization. Any means of collecting and organizing data is a database. Prior to the Information 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 job title of those who had