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 tutorial site lists commonly-used SQL statements, and is divided into the following sections:

• SQL Commands : Basic SQL statements for storing, retrieving, and manipulating data in a relational database. Beginners should start with this section.
• Advanced SQL : Discusses SQL commands and calculations that are more advanced.
• SQL Functions : Commonly-used math functions in SQL.
• SQL String Functions : Common string functions used in SQL.
• SQL Date Functions : Common date functions used in SQL.
• Data Definition Language (DDL) : Commands used to create, modify, and delete database objects.
• SQL Constraint : Commands that limit the type of data that can be inserted into a column or a table.
• SQL ALTER TABLE : How to change the structure of a table after it is created.
• SQL NULL : Discusses the concept of NULL in SQL and functions associated with the NULL concept.
• SQL Video Tutorial : For those who prefer to watch videos to learn, the 1Keydata team has created several video tutorials on SQL.
• SQL Syntax : A single page that lists the syntax for all the SQL commands in this tutorial.
• SQL Quiz : A 25-question quiz that you can use to see if you have understood the concepts taught in this tutorial.

For each command, the SQL syntax will first be presented and explained, followed by examples. 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.

Although it is a good idea to go through this tutorial in the above order, especially for beginners, 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.