What is SQL? SQL is the computer language used to store and manipuate data in a relational database management system (RDBMS).
SQL was first developed by IBM in 1974, and was initially called SEQUEL (Structured English Query Language). In 1979, Relational Software (now Oracle) released the first commercially available version of SQL (for VAX). Since then, a number of vendors released their own flavors of SQL. The first SQL standard was published by the American National Standards Institute (ANSI) in 1986 and was aptly named SQL-86. It has since gone through several revisions:
Currently the SQL standard is being released by the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC).
The basics of SQL have not changed much after SQL-92. Different RDBMS vendors employ different flavors of SQL, which may or may not adhere to any of the standards, though for the most part the basics of SQL are preserved.
Compared to other computer languages, SQL is relatively easy to learn. The big advantage of SQL is that it's syntax is something that an English-speaking novice can easily understand. Let's consider the following SQL statement:
SELECT Student_Name, Score
WHERE Score < 60;
It's straightforward to see that the purpose of this SQL statement is to get the student name and that student's score for scores that are below 60 from the Score_Details table.
Let's take a look at a more complex example: If, instead of getting a list of all scores less 60, we want to get a list of students whose total score is above 200, listed from the highest score to the lowest. We would use the following SQL:
SELECT Student_Name, SUM(Score)
GROUP BY Student_Name
HAVING SUM(Score) > 200
ORDER BY SUM(Score) DESC
Additional SQL references: