Structured Query Language (SQL) is used to query, modify, and control data in a relational database system. IBM first developed SQL in the 1970s and many versions of SQL exist today.
Some of the more common relational database management systems that use SQL are Microsoft SQL server, Sybase, and Oracle.
SQL statements allow your applications to programmatically retrieve
data in a database.
The query is the fundamental concept of SQL. A query is simply a request for information from a database. While a query can get all the information in a database, it is frequently structured to request only records that meet a certain criteria.
Queries can be applied to a single database table as well as multiple tables.
In addition to retrieving data, you can use SQL statements to update, insert, and delete records.
Although it can be used on a single stand-alone machine, SQL is most commonly used in a client/server architecture.
The client submits a request for data to the server. The server processes the request and returns results, if any, to the client. Also note that in this model there can be more than one server handling requests.
You will begin to get first-hand experience using SQL statements in the next Module.
In the next lesson, you will learn how to set up the data environment.