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Monday, 23 June 2008

Database Basics and Jargon

What is a Database ?

A Database is basically a computerized record keeping system, whose overall purpose is to maintain the information on it and to make that information available on demand.
It can be from your video collection to members of your website, etc is a collection of data in a structural manner.

Database dialect

Here's a quick guide to some of the more common database terms.

database: A collection of related information stored in a structured format. Database is often used interchangeably with the term table (Lotus Approach, for instance, uses the term database instead of table). Technically, they're different: a table is a single store of related information; a database can consist of one or more tables of information that are related in some way. For instance, you could track all the information about the students in a school in a students table. If you then created separate tables containing details about teachers, classes and classrooms, you could combine all four tables into a timetabling database. Such a multi-table database is called a relational database.

data entry: The process of getting information into a database, usually done by people typing it in by way of data-entry forms designed to simplify the process.

dbms: Database management system. A program which lets you manage information in databases. Lotus Approach, Microsoft Access and FileMaker Pro, for example, are all DBMSs, although the term is often shortened to 'database'. So, the same term is used to apply to the program you use to organise your data and the actual data structure you create with that program.

field: Fields describe a single aspect of each member of a table. A student record, for instance, might contain a last name field, a first name field, a date of birth field and so on. All records have exactly the same structure, so they contain the same fields. The values in each field vary from record to record, of course.

flat file: A database that consists of a single table. Lightweight database programs such as the database component in Microsoft Works are sometimes called 'flat-file managers' (or list managers) because they can only handle single-table databases. More powerful programs, such as Access, FileMaker Pro and Approach, can handle multi-table databases, and are called relational database managers, or RDBMSs.

index: A summary table which lets you quickly locate a particular record or group of records in a table. Think of how you use an index to a book: as a quick jumping off point to finding full information about a subject. A database index works in a similar way. You can create an index on any field in a table. Say, for example, you have a customer table which contains customer numbers, names, addresses and other details. You can make indexes based on any information, such as the customers' customer number, last name + first name (a composite index based on more than one field), or postal code. Then, when you're searching for a particular customer or group of customers, you can use the index to speed up the search.

key field: You can sort and quickly retrieve information from a database by choosing one or more fields to act as keys. For instance, in a students table you could use a combination of the last name and first name fields as a key field. The database program will create an index containing just the key field contents. Using the index, you can quickly find any record by typing in the student's name. The database will locate the correct entry in the index and then display the full record.

primary key: A field that uniquely identifies a record in a table. In a students table, a key built from last name + first name might not give you a unique identifier (two or more Jane Does in the school, for example). To uniquely identify each student, you might add a special Student ID field to be used as the primary key.

record: A record contains all the information about a single 'member' of a table. In our students table, each student's details (name, date of birth, contact details, and so on) will be contained in its own record.

relational database: A database consisting of more than one table. In a multi-table database, you not only need to define the structure of each table, you also need to define the relationships between each table in order to link those tables correctly.

table: A single store of related information. A table consists of records, and each record is made up of a number of fields. You can think of the phone book as a table: It contains a record for each telephone subscriber, and each subscriber's details are contained in three fields – name, address and telephone.

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