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SQL etc

Posted Jul 26, 2001

Beginning SQL Programming: Pt. 2 - Page 2

By DatabaseJournal.com Staff

SQL's Place in the Data Center

So how does SQL actually fit into the solution to my data management problems? We discussed earlier that SQL did not have a front end (user interface) or a back end (DBMS). So in the next few sections we will discuss some "ends" that we can use as well as the protocols that create a bridge across which the SQL statements flow.

"How Do I Get SQL? "

You need a front end that can connect to a SQL-enabled DBMS and can pass a SQL statement. We will talk more about connections in Chapter 2, but for now consider a connection to be a conduit for carrying SQL statements between the front and back ends. A connection is like the apparatus of the telephone company that connects your handset to your friend's handset – it allows a language to be used to communicate. Third, you need a SQL-enabled DBMS. You probably already have a SQL-enabled front end and a DBMS in one form or another (see the sections below). And if you don't you can get an inexpensive version or a trial version that will allow you to get started learning SQL for free. Keep in mind that since SQL is a standard in the public domain, you do not need software or a license to use the language. You can acquire SQL by simply learning the syntax of how to write the SQL statements. But in order to practice creating and running SQL statements you will need three parts:

  • a front end
  • a connection
  • a back end

We will look in detail at various options for each of these, but let us start with a quick overview.

The front end provides a means to send a SQL statement. Usually the front end includes an interface to users with a form to gather data and buttons to carry out tasks. The front end may contain a fixed SQL statement or it may use code to create a statement on the fly using the data provided by the user. The most common type of front end is the web browser.

The connection provides a conduit to get the SQL statement to the back end and then to return results to the front end. The connection is like a telephone connection over which a spoken language travels, although the language itself is free. A common connection today is ADO (Activex Data Objects) but there are many other options.

The back end is a DBMS that accepts and can act on SQL statements. Usually the back end has two parts, the actual store of data and a database engine, which can carry out the SQL statement. The most common back ends are the major database products such as Oracle and Microsoft SQL Server.

placement of front end, back end, and connection

The included CD contains a front end, connection and back end, but in a less conventional arrangement than the one we have just described. The CD is a 120-day trial version of Microsoft SQL Server 2000. SQL Server provides a very strong back end, but it does not come with front end or connection software. However, there is a utility called Query Analyzer which comes with SQL Server. This tool provides a front end optimized for developers that want to test SQL statements. It is a very simple front end that allows you to type a SQL Statement, run it and then view the results. A normal front end would have tools for creating a polished interface for users, but Query Analyzer is aimed at developers that are testing. Built into Query Analyzer is connection software that automatically creates a connection when the developer selects which database to work with.

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