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1、外文原文Introduction to SQL ServerBy SamuelRelational databases have been around for 30 years, but they were not the original kind ofdatabase, nor are they the newest kind of database. XML and object-oriented data structures haveevolved in recent years. But relational databases are still by far the most
2、 popular kind of database available and will be for some time to come.SQL is the abbreviation of Structured Query Language and it is for relational databases, as the title indicates this is only for fresher who has just started the carrier or who is waiting to open up the carrier in the application
3、programming side. But that does not mean this article is a tutorial for a fresher who does not know anything about SQL.This article is meant for who already have a little knowledge in SQL and want toimprove it.What Does SQL Do?First, SQL is the premier tool for viewing information from a relational
4、database. It doesnt just give you a data dump. SQL gives you sophisticated tools to summarize, consolidate, and calculate from the data. Using table relationships, data can be combined from multiple tables in a number of ways. With a properly designed database, SQL can answer practically any questio
5、n about the data.Second, SQL provides commands to manipulate the data in a relational database. Records can be updated and added to or deleted from a table. Here is SQL as a database language really shines. Procedural programming languages, such as BASIC, might require several lines of code to updat
6、e a record in a database table. In addition, procedural programming languages would have to use some sort of looping structure to repeat this process on every record. SQL operates on an entire set of records all at the same time. SQL is like haiku for programmers; often a dozen words or fewer can de
7、lete or change thousands of records.Finally, SQL is a complete data definition language (DDL). The database itself can be created along with all tables, fields, primary keys, and relationships. Add to that the record insert commands, and you can have a complete database and all its data expressed in
8、 programming code. This greatly enhances a database programmers ability to work remotely or to port data enhancements among various installations.The prerequisite for learning SQL is knowledge in Discrete Mathematics (Set Theory,Relations and Functions). Although it is not necessary to learn all the
9、 theorems and proof for the theorems in the Discrete Mathematics, you should have learned the basic concepts of the Sets, Relations and Functions. This will help you to learn SQL queries and fundamentals easily. If you want to explore a RDBMS more deeply you should learn Graph Theory too.Although I
10、tried to avoid SQL Server specific topics in this article, I am sure that some topics are pure to SQL server such as SQL Enterprise manager.Data to DBMSData is something that should be stored for future manipulations (In terms of Database). The system which provides such a facility is called Databas
11、e Management System or DBMS.The simplest form to store a data for latter retrieval is using a text file. For example you may want to store your friends name and phone numbers to use it latter. (In this case you may use notepad or word to do so.) This kind of storage is called flat file storage or un
12、structured storage. In this case the text editor uses the File and Directory services provided by the Operating System to accomplish the task of storing and retrieving data.But these unstructured flat files are not suitable to large data such as storing stock details. Since the stock data is large i
13、n volume and added and updated frequently it is not scale up well if we use a simple flat file. To overcome this we need some system which should perform the storing, retrieving, manipulating and querying operations on the data and give output to us. This kind of system is called Database Management
14、 System. So a DBMS is a system which organizes and stores data in a structural way for fast retrieval. A DBMS uses one or more files to store the given data.Since the DBMS is meant mainly for developers every DBMS has it is own language to write the commands. The languages are standardized under the
15、 name SQL(Structured Query Language). The following definition for SQL is from Books Online“A language used to insert, retrieve, modify, and delete data in a relational database.SQL also contains statements for defining and administering the objects in a database. SQL is the language supported by mo
16、st relational databases, and is the subject of standards published by the International Standards Organization (ISO)and the American National Standards Institute (ANSI). SQL Server 2000 uses a version of the SQL language called Transact-SQL.”Representation of Data by DBMSDBMS should represent the data stored by them in some form and it is most common to represent them as Column, Row, Tables and Databases. As you know SQL you know what are columns, rows, tables and database.Primary KeyA co
