Structured Query Language (SQL)

Relational databases are accessed using the Structured Query Language (SQL). SQL is the ANSI standard language for accessing relational databases. Unlike the Java language, which can do just about anything, the SQL language was designed for a single purpose: accessing data from databases. In an RDBMS, the SQL engine performs the real work behind the scenes. The engine accepts queries in the form of SQL code statements. The queries are submitted from a client application to the database server. The SQL queries are received by the database, and a fast path to the requested data is formulated. Finally, requested data is returned to the client. Sometimes, the query or the result can be cached, making future queries even faster. Typically, the queries are submitted from remote machines via network protocols. However, they can be local API calls via DLLs, often called embedded databases. There are a few different methods, which will be covered in more detail later, for communicating between a Java application and the database.

The SQL language itself is very flexible, supporting everything from simple to complex queries. These queries can be formed in a variety of ways. Mastering the SQL language takes time. To truly use the speed, power, and potential the database has to offer, advanced SQL concepts must be learned and utilized. Understanding the SQL language will also greatly improve your understanding of database structure and design. A good comprehension of the language used to access the data will give a better perspective on how the data should be organized. The data should be structured in such a way that the database can search it and traverse through it effectively. Creating efficient and intelligent queries is the key to getting the most out of database performance. Well-written SQL statements running against a well-structured database will significantly speed up database response time, allowing the database to support more concurrent users. This then allows for the fetching of more data more often, because data isn’t stored or accessed redundantly or wastefully. A developer’s knowledge and skill in the SQL language can have a tremendous impact on the performance of the database, as well as the system overall. SQL syntax differs slightly among databases. However, the differences are usually minor, often in the form of extensions, shortcuts, and convenience features. ANSI-standard SQL will work with most databases.