### Using SQL and SQL databases

Perhaps the most popular and most powerful database formats are DBMS applications based on the Structured Query Language (SQL). SQL databases usually work over a client/server network architecture, providing an SQL Server to create, store, and manipulate database files, tables, fields and records, and an SQL Client interface allowing workstation users not only to design and work with database files, but also to retrieve useful and meaningful data that will help them in their everyday work.

#### What is SQL?

SQL is a query language designed for organizing, managing, developing and querying large relational databases over computer networks. SQL is a common language in the Information Science (IS) and Information Management industry. The language has been standardized by the American National Standards Institute (ANSI) and the International Standards Organization (ISO), meaning that there are specific features that must be present in any version of SQL produced by a software company in order for that version to be officially called SQL. Many software vendors add more advanced features to their version of SQL in an effort to improve the language and attract customers, but it must retain the original standards established by ANSI and ISO.

SQL is not a true computer language. It cannot be used to create stand-alone computer applications or operating systems. SQL is often referred to as a sub-language, since it can be used within other languages or applications. Most importantly, the purpose of the SQL language is specific to working with relational databases.

The syntax of the SQL language is built on a system of sending SQL statements to the SQL database server. Each statement is a request to perform a database operation, such as creating a database file, adding tables and fields to a database, adding records to tables, or retrieving data from databases. The SQL server analyzes the SQL statement and performs the required operation. For example, if the statement is a request for data, the server gathers the data and returns it to the client workstation for the user to view.

An SQL query is an SQL statement designed specifically to request data from one or more SQL databases. Some SQL applications require that you type in an SQL query directly using a text editor, while others provide graphical user interfaces that lead you through the process of querying an SQL database. In the latter case, the application must create an SQL statement based on the information you provide. This statement is the actual SQL query, and it is the SQL query that is used to request the data. Seagate Crystal Reports falls into this second category of SQL-compliant applications.

##### Client/server architecture

One of the most powerful features of SQL DBMS applications is their ability to efficiently use the client/server architecture of a network.

A simple network structure consists of one or more network servers that provide a common location where all users on the network can obtain data and applications. Many network servers also provide network security, automated services such as backing up data, and network resource monitoring to provide the best service possible to all workstations on the network. Because of the high processing demands required by a network server, the computer used as the server is often a high-powered, fast machine that may contain multiple processors, multiple hard drives, and multiple CD-ROM drives.

A network client is a single computer workstation that is used regularly by one or more company employees. A user works on the client and accesses data and applications from the server over the network. Large processing jobs that require a lot of time and resources are handled by the server, and the finished results are sent back to the client. This provides more efficient time management for users because the local workstation has less processing time and more "up" time available to the user.

Many modern computer applications are based on this client/server architecture. A simple client/server application has two parts: a server-based application that is located on a network server machine, and a client-based application that is located on a user's workstation. The server application handles complex, time-consuming, or power-demanding processes, taking advantage of the network server's power and resources, while the client application provides an easy-to-use user interface designed to help get the work done faster and better than it could otherwise be done.

Often, a client/server application will be available with a certain number of seats, depending on the cost of the application. Each seat represents either a single client workstation, or a single client user (depending on the software vendors' specifications) that can be connected to the client/server software. Software vendors often sell additional seats for their applications, each seat coming with a complete set of client application software.

Do not confuse server applications with network server computers. Both are often referred to as servers. However, a server application resides on a network server, taking advantage of the hardware and operating system capabilities of the server machine, while a network server is a physical machine to which network clients are connected by cables or some other connection device.

Seagate Software, Inc. http://www.seagatesoftware.com Please send comments to: techpubs@seagatesoftware.com