Lab%209%20-%20Introduction%20to%20Structured%20Query%20Language

Lab%209%20-%20Introduction%20to%20Structured%20Query%20Language

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L AB 9 I NTRODUCTION TO S TRUCTURED Q UERY L ANGUAGE WHAT IS SQL AND WHY SHOULD I CARE? SQL, or Structured Query Language, is a language that is used to manipulate and report the data in relational databases. It can be pronounced either by its letters (Ess-Que-Ell) or as a word (See-quel). SQL is an open standard database language, supported by ANSI (American National Standards Institute). That means that SQL does not just work with Microsoft Access or even with just Microsoft products. Oracle, Sybase, Microsoft SQL Server, MySQL, IBM DB2, Microsoft Access, and Lotus Approach, and many others all support SQL. More than 100 database management products, running on everything from PCs to mainframes, support SQL. SQL provides three major kinds of functionality. First, SQL is the tool of choice for viewing information from a relational database. SQL doesn't just give you a simple list of the data. It also provides sophisticated tools to calculate from the data, summarize data, and consolidate 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 question about the data. Second, SQL provides commands to manipulate the data in a relational database. Records can be added to a table. Records can be updated with new information. Records can be deleted. Finally, SQL is a complete data definition language (DDL). The database itself can be created along with all tables, fields, primary keys, and relationships. SQL can also define users and set security permissions. In these labs we will just scratch the surface of how to view information with SQL. But it is nice to know that the language extends far enough to handle practically anything you want to do with a database. SQL VS. QBE Not that SQL is the only way to manipulate a database. Most systems also have their own visual Query by Example (QBE) interface. Often the QBE interface is more user-friendly. CNIT 180: Lab 9 – Introduction to Structured Query Language Page 1
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Despite that fact there are at least three good reasons why anyone whose career will involve working with information systems would want to learn some SQL. 1. While QBE varies widely among databases systems, SQL, as an ANSI standard, varies only slightly. When you learn SQL for one database system, you have learned most of the SQL you need for any database system. 2. Some queries cannot be done in QBE. For sophisticated sub-queries, unions, and other kinds of queries, SQL is the only tool in town. 3. For many kinds of jobs knowledge of SQL is an essential skill. Database administrators use SQL as the primary language for manipulating the database. Programmers use SQL to communicate with the database in their web
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This note was uploaded on 01/30/2012 for the course CNIT 180 taught by Professor Victorbarlow during the Spring '12 term at Purdue University.

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Lab%209%20-%20Introduction%20to%20Structured%20Query%20Language

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