What is SQL? All you need to know about Structured Query Language

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© iStock

From common uses to the different commands and courses, here's all you should know about SQL

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Structured Query Language (SQL) is a programming language designed for database management and manipulation – primarily used to find and pull information from large databases.

SQL is normally displayed on relational databases, a form of database derived from Edgar F. Codd's relational model of storing information in way that makes it accessible and identifiable in relation to other information in it.

The language was developed at IBM by Donald Chamberlin and Raymond Boyce in 1974, where it was initially named SEQUEL (Structured English Query Language), building on Edgar F. Codd’s relational model.

SQL contains four main categories, with an additional two commands that are mostly used for computer databases, and has since been integrated with more features after becoming a standard of the American National Standards Institute (ANSI) in 1986 and International Organisation for Standardisation (ISO) in 1987.

SQL is a fourth-generation language, meaning commands are close to human language. By contrast, the Java and C++ programming languages are third-generation languages that are more abstract to the untrained eye.

Read next: The best NoSQL database options for the enterprise

What is SQL and how does it work?

SQL has become the industry standard for manipulating and querying data in a relational database. The uses of the language are broken into three other components aside from writing queries. These are:

Data Manipulation Language (DML), which is used to manipulate database content in retrieve, update, delete and insert modes. The DML has four commands that can be used to manipulate the information which is the Select, Insert, Update and Delete commands.

Data Definition Language (DDL) is used to manage tables and index structures, also with synchronised commands that can be used to create, alter and delete database tables.

Data Control Language (DCL) is often used to manage who can access the database, providing rights to certain users. The two commands that come with this are Grant and Revoke, which are the two core commands of relational database security and authentication.

Data Query Language (DQL) is similar to DML, as it is used to select, insert, update and delete data from the database. The two can be used together.

The other SQL commands are data administration and transactional control commands.

The commands, also known as statements, can be used for different processes such as control of transactions, connections, and diagnostics. With this, the database server processes the inputted command and responds to the user’s command.

SQL Standard

The SQL standard has been through several changes since the initial years, mostly to add new features to the standard structure.

For instance, SQL standard can now support XML, regular expression matching and more. SQL is used across popular database applications on the internet today such as Oracle Database.

A lot of the added databases like MySQL and PostgreSQL do not implement the whole SQL standard; instead, vendors decide to add their own structure to the database.

Some vendors have added their own flavors and variations to the SQL standard, the main ones being IBM, Microsoft and Oracle.

Variations

Microsoft developed its own relational database management system in 1989, named Microsoft SQL Server.

It was designed to support a range of transaction processing, business intelligence and analytics applications in IT environments. The server is combined to Transact-SQL (T-SQL), which is an implementation of SQL from Microsoft to add proprietary programming extensions to the SQL language.

There are multiple versions of the SQL Server, with various integrations of data management and analytics tools, along with newer technologies like cloud computing and reports on mobile devices.

Microsoft SQL Server 2016 was the first one developed as part of its ‘mobile and cloud first’ technology strategy, and also included performance tuning, real-time operational analytics, and data visualisation.

The current version, SQL Server 2017, is available on Windows and Linux operating systems. It also supports Python programming language and the initial SQL Server R services were renamed as Machine Learning services and expanded to run both R and Python applications.

Oracle also provides SQL, which can be used for accessing, defining and maintaining data. Its SQL server can be used in collaboration with Oracle, PHP, Java and other programming languages.

It also offers Oracle SQL Developer, which is an integrated development environment (IDE) that was launched in 2006 for developers working with SQL in Oracle databases.

Read more: Best cloud-based relational database options for the enterprise

Online SQL Courses

As one of the most sought-after programming languages in the UK, having knowledge of SQL could really boost your career.

Although SQL might appear complicated, there are some great online courses available to help.

Here are some suggestions:

The Complete SQL Bootcamp – Priced at £11.99, this online course by Udemy provides multiple lectures for those that wish to learn read and write complex queries using PostgreSQL. It is available in five languages, including English, Japanese and Spanish.

The Complete Oracle SQL Certification Course – Also available on Udemy, this provides over 30 lectures to help people become job ready with the SQL language. It is £11.99 and available in English, Portuguese and Spanish.

Microsoft SQL for Beginners – This course basically provides a selection of lectures for people to learn how to complete SQL queries using Microsoft’s SQL Server and T-SQL. It is also £11.99.

SAP HANA SQL & SQL Scripting – A comprehensive course of 65 lectures on how to develop SAP HANA database skills and SQL scripting. It is available at £13.99.

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