Summary of this lesson The lesson summary is only provided for a rapid preview or review of the material. It is not intended as a substitute for the fuller treatment provided by lectures and in on-line topic readings. DBMS Query Languages and SQL Database query facilities provide users with an ability to access a database and extract needed information arranged in a way that suits the user's need. With non-procedural languages, users do not have to explain the detailed logical steps, but need only specify what action or output they desire. An SQL statement is a command that orders the DBMS to perform some operation such as adding, modifying, or simply viewing the contents of a database.
Users can either manipulate data in physical files or in virtual tables called user views.
Select Command Data in a relational database is placed into database tables which contain data concerning some database entity , such as customer or a product attributes . The rows contain information about some unique instance of the entity such as a particular customer or product. The columns provide information about the attributes of the particular entity. Data about entities have certain characteristics such as the physical format in which they are stored. These characteristics are often referred to as data properties .