What is database?
- Database is an organized collection of information about an entity having controlled
redundancy and serves multiple applications.
- DBMS (database management system) is an application software that is developed to create and manipulate the data in database.
- A query language can easily access a data in a database. SQL (Structured Query Language) is language used by most relational database systems.
- IBM developed the SQL language in mid-1979.
- All communication with the clients and the RDBMS, or between RDBMS is via SQL. Whether the client is a basic SQL engine or a disguised engine such as a GUI, report writer or one RDBMS talking to another, SQL statements pass from the client to the server.
- The server responds by processing the SQL and returning the results. The advantage of this approach is that the only network traffic is the initial query and the resulting response. The processing power of
the client is reserved for running the application.
SQL is a data sub-language consisting of three built-in languages:
Data definition language (DDL),
Data manipulation language (DML) and
Data control language (DCL).
It is a fourth generation language. SQL has many more features and advantages. Let us discuss the SQL in more detail in this unit. It should be noted that many commercial DBMS may or may not implement all the details given in this unit.
in other words, you can say that:
A database program is a type of computer software that is designed to handle lots of data, but to store them in such a way that finding (and thus retrieving) any snippet of data is more efficient than it would have been if you simply dumped them willy nilly all over the place.
With such a database software, if you (say) keep a list of customers and their shipping addresses, entering and retrieving information about your one millionth customer will not take much longer (if at all) than entering and retrieving information about your 1st customer.