Question: What is SQL?

by | June 24, 2014 3:15 pm

   Answer:

   SQL is a computer language used to work with databases.

   SQL is an acronym for Structured Query Language. It is pronounced either as the three separate letters S Q L or as “see quell.” Both pronunciations are used.

   Databases are how large amounts of data are stored on a computer and the associations of the information within the database. It is set up in tables. For instance, in student records database, there may be a table containing student identification information such as student number, name and address. In another table will be classes and would have the various classes a school offers, who teaches them and the name of the class. A third table may contain student classes, which has class numbers and the student numbers of the students in the class. The third table is linked to the first table by student numbers.

   The most common types of databases you will encounter are Access, Oracle, SQL Server and MySQL. Access is a personal database system that is part of Microsoft Office. MySQL, Oracle and SQL Server can be run on personal computers (free versions for personal use are available) but are designed to work with large databases of information on large machines. This is why businesses like Red9 exist, they are designed to increase the speed of SQL servers. MySQL is an open source database that I use for several web sites I maintain. Oracle is made by Oracle (you may remember them as a sponsor of the team in the America Cup sailing event,) and Microsoft makes SQL Server.

   You would use SQL to write statements to tell the computer to retrieve information from the database. It is command type language and does not usually involve complex programs to get the information, although they can be written. The SELECT statement is used to get information form a database and is the most common SQL statement. To get a student name and grade from the database the statement may be SELECT studentinfo.student_number, student_name, grade where studentinfo.student_number = classes.student_number; What that says is find where the student number in student information table matches the student number in the classes table and give us the student number, name and grade.

   SQL is language that was originally developed with databases back in the early 1970s and is still used extensively to get information from databases to make available to us as users on paper, on the Internet or just in an organization on the screen.

   The computer departments at colleges and technical colleges teach courses in using SQL.

   Send me your questions about computers to me at the paper or to my e-mail dwight@dwightwatt.com and tell me you read this in this paper. I will pick a question to answer each week. 

   Dwight Watt does computer work for businesses, individuals and organizations and teaches about computers at a college. His webpage is www.dwightwatt.com His e-mail address is dwight@dwightwatt.com.

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