A subquery places one query inside another one. The second query resides somewhere within the WHERE clause of a SELECT statement. One or more values returned by the subquery are used by the main query to return the results to the user Subquery: A query that is embedded in a main, or parent, query and used [...]
Continue reading → The computer industry suppliers can be classified into three groups , namely Hardware Suppliers, Software Suppliers and Service Suppliers. Suppliers of hardware include Mainframe manufacturers , peripheral vendors, computer leasing firms and used –system dealers. IBM is one of the major suppliers of mainframe computers. Peripheral vendors supply tape drivers, disk and diskette drives, printers [...]
Continue reading → There are three things one can do to prevent virus infection in a computer system. These are: 1. Limit sharing 2. Limit transitivity 3. Limit functionality Limit sharing One can limit sharing by limiting information flow so as to form a post office kind of communicating information domains in a network system. In such a [...]
Continue reading → An audit trail is designed to permit tracing of operation, whether it is related to insertion, deletion or updation of records or processing performed on the computer system. In audit trail, all the operations that a user performs during a log-in session are noted. When a user logs in, the system records the user’s account [...]
Continue reading → A benchmark is a sample program used for evaluating the performance of computer-based systems. It helps in the following manner: 1. Determination of the minimum hardware configuration needed t operate the system. 2. Testing the system in an ideal environment to determine comparative timings and then testing the system in a normal environment. 3. Determination [...]
Continue reading → The pictorial representation of information and instructions using GUI’s are more user-friendly and easy-to-understand than textual commands and lifeless screens. Nowadays, GUI (Graphical user Interface) is incorporated within most of the computer operating systems, pioneer among them being the Microsoft’s Windows 9X,2000 and XP. Note : GUI is a software design that allows you to [...]
Continue reading → In the system design process, the primary objective is to identify user requirements and to build a system that satisfies these requirements. Design of system is largely the logical design. The logical design can be sketched on a paper or on a computer terminal. The design, also including the physical design elements, describes the data [...]
Continue reading → Systems are designed to perform certain required functions – there could be new functions, or modifications of older functions. A system which is being designed will often require changes and re-orientation in the way an organization works. There could be changes in format of input, or reports, additional information to be gathered, new procedures to [...]
Continue reading → Equijoins are also commonly known as simple joins, or inner joins. Given two or more tables, an equijoin will return the results of these tables where a common column between any given pair of tables has the same value (an equal value). Equijoins are typically joins between foreign keys in one table to a primary [...]
Continue reading → So far, we have been dealing with only one table at a time in our SQL query examples. But typically the information needed to satisfy a user query requires more than one table. In new SQL 1999, you can not only join two or more tables in a number of different ways, but can also [...]
Continue reading → An interpreter is a translating program for the purpose of converting high level language into machine level language. An interpreter translates only one statement of a high level language at a time. After translation the statement is immediately executed. This is in contrast to the compiler which translates the entire source program into object program. [...]
Continue reading → A readymade program is known as utility. An editor is also a utility for creating and modifying text through the user terminal. The text may be any document, program in any computer language or data required by the program. Generally the text is stored on the disk as a file using a filename. An editor [...]
Continue reading → Everyone today must be aware of the fact that the computer only understands machine language. So a program written in high level language needs to be translated into machine language before it can be executed by the computer. This job of translation is done with the help of the software program. This program in case [...]
Continue reading → System Analyst has the following duties to perform : Estimate personnel requirements, cost and time for system’s implementation. Review and approve proposed system’s solutions Perform resource planning and scheduling for system’s personnel. Develop, implement and enforce procedural standards for performing tasks of system analysis and design. Evaluate performance of system’s personnel and report on personnel [...]
Continue reading → A Linux shell is the program which interprets what you type on the command line and decides what to do with that. A shell can be invoked in a non-interactive way, for example to execute a pre-typed list of commands contained in a text file (a “shell script”). Think of a shell as the equivalent [...]
Continue reading →