SQL Tutorial - Learn SQL Query Language
SQL (Structured Query Language) is a computer language aimed to store, manipulate, and query data stored in relational databases. The first incarnation of SQL appeared in 1974, when a group in IBM developed the first prototype of a relational database. The first commercial relational database was released by Relational Software (later becoming Oracle).
Standards for SQL exist. However, the SQL that can be used on each one of the major RDBMS today is in different flavors. This is due to two reasons: 1) the SQL command standard is fairly complex, and it is not practical to implement the entire standard, and 2) each database vendor needs a way to differentiate its product from others. In this tutorial, such differences are noted where appropriate.
The advent of Big Data has brought even more variety to SQL. Initially Big Data technology was geared towards programmers. However, soon Big Data vendors realized they need to provide a SQL-like layer so analysts can query into the data set, and they started to offer their own versions of SQL. The biggest difference between these types of SQL and the SQL that runs on top of relational databases is the former lacks the ability to manage data at the row level. For example, updating a row is not possible. In this tutorial, we will point out how the two most popular Big Data SQL implementations, HiveQL (Hive's version of SQL) and SparkSQL (Spark's version of SQL), are different from traditional SQL.
This SQL programming help site lists commonly-used SQL statements, and is divided into the following sections:
For each command, the SQL syntax will first be presented and explained, followed by an example. By the end of this tutorial, you should have a good general understanding of the SQL syntax, and be able to write SQL queries using the correct syntax. My experience is that understanding the basics of SQL is much easier than mastering all the intricacies of this database language, and I hope you will reach the same conclusion as well.
Although it is a good idea to go through this tutorial in the above order, it is not required. You are free to go through the site based on how you learn best. Please bookmark this site now and so you can come back to this site whenever you need to remember how a SQL command is used.