A database is an organized collection of data. The data is typically organized to model relevant aspects of reality (for example, the availability of rooms in hotels), in a way that supports processes requiring this information (for example, finding a hotel with vacancies). A general-purpose database management system (DBMS) is a software system designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs include MySQL, PostgreSQL, SQLite, Microsoft SQL Server, Microsoft Access, Oracle, Sybase, dBASE, FoxPro, and IBM DB2. A database is not generally portable across different DBMS, but different DBMSs can inter-operate by using standards such as SQL and ODBC or JDBC to allow a single application to work with more than one database. Formally, the term "database" refers to the data itself and supporting data structures. A "database management system" (DBMS) is a suite of computer software providing the interface between users and a database or databases. Because they are so closely related, the term "database" when used casually often refers to both a DBMS and the data it manipulates. Outside the world of professional information technology, the term database is sometimes used casually to refer to any collection of data (perhaps a spreadsheet, maybe even a card index). This article is concerned only with databases where the size and usage requirements necessitate use of a database management system. The interactions catered for by most existing DBMS fall into four main groups: * Data definition. Defining new data structures for a database, removing data structures from the database, modifying the structure of existing data. * Update. Inserting, modifying, and deleting data.
* Retrieval. Obtaining information either for end-user queries and reports or for processing by applications. * Administration. Registering and monitoring users, enforcing data security, monitoring performance, maintaining data integrity, dealing with concurrency control, and recovering information if the system fails. A DBMS is responsible for maintaining the integrity and security of stored data, and for recovering information if the system fails. Both a database and its DBMS conform to the principles of a particular database model. "Database system" refers collectively to the database model, database management system, and database.
Microsoft Access, also known as Microsoft Office Access, is a database management system from Microsoft that combines the relational Microsoft Jet Database Engine with a graphical user interface and software-development tools. It is a member of the Microsoft Office suite of applications, included in the Professional and higher editions or sold separately. Microsoft Access stores data in its own format based on the Access Jet Database Engine. It can also import or link directly to data stored in other applications and databases.
A primary key is a unique identifier for a database record. When a table is created, one of the fields is typically assigned as the primary key. While the primary key is often a number, it may also be a text field or other data type. For example, if a database contains definitions of computer terms, it would make sense that each term is only listed once in the database. By defining the "Term" field as the primary key, it would ensure that no term is listed more than once in the database. While a table's primary key is usually assigned to a specific field, it can also be comprised of multiple values. For example, a database of news articles might use both the title and date fields to uniquely identify each entry. By combining the "Title" and "Date" fields as the primary key, it would ensure no entries have the same title on the same day. If multiple fields in a table cannot have duplicate values, most database management system (DBMS) also allow fields to be defined as "Unique." This is...