Top 10 Best SQL Courses on Udemy [2021 REVIEWS]

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sql courses

Udemy is a popular marketplace for affordable courses on a huge range of subjects. This includes high-quality options for anyone looking to learn programming and SQL .

However, with so much choice it can be difficult to know which course to go for. Well, we are here to help.

In this top 10 review round-up, we have carefully selected 10 of the best SQL courses currently running on Udemy in 2021.

Whether you are an expert looking to develop your skills further, or a beginner wanting to learn the basics (and other needs in between) you will find something here to suit you.

For our top choice SQL courses at a glance, just head to the table below. For an in-depth review of each of the selected courses, keep on reading.

Best SQL Courses on Udemy

COURSE

TITLE

DETAILS

OUR RATING

BEST BEGINNER COURSE

Complete SQL Bootcamp 2021

9hrs of video
13 Resources

14 Articles
Lifetime Access
Certificate

Ultimate MySQL Bootcamp

20hrs of Video

141 Articles
4 Resources
Lifetime Access
Certificate

BEST DATA VISUALS

Complete Bootcamp for SQL and Data Visualization

5.5hrs of video

2 Resources
Lifetime Access
Certificate

Complete Developer’s Guide using SQL and PostgreSQL

22hrs of video

9 Articles

46 Resources
Lifetime Access
Certificate

BEST FOR MICROSOFT SQL

Microsoft SQL for Beginners

3.5hrs of video
13 Resources
Lifetime Access
Certificate

BEST FOR INTERMEDIATES

 Project-Based SQL Course

6.5hrs of video
9 Resources

Lifetime Access
Certificate

BEST BUSINESS FOCUSED

SQL and Data Analytics Applications in the Real World

8.5hrs of video
2 Resources
Lifetime Access
Certificate

BEST SERVER FOCUSED

SQL Server Performance Tuning – Part 1

6hrs of video
7 Resources
Lifetime Access
Certificate

BEST EXPERT LEVEL

SQL Expert Certification Preparation

13hrs of video
6 Resource

7 Articles
Lifetime Access
Certificate

SQL Advanced and Expert Certification Preparation Course

4.5hrs of video
21 Resources

7 Articles
Lifetime Access
Certificate

The Reviews

sql

The following reviews focus on 10 of the best SQL courses that are currently being offered on Udemy.

Best SQL Courses for Beginners

1. BEST BEGINNER COURSE: Complete SQL Bootcamp 2021

The Complete SQL Bootcamp 2021: Go from Zero to Hero

This is a popular complete SQL on-demand course designed for beginners who want to learn SQL so as to manage databases, as well as perform data analysis using SQL.

As a beginner course, the student is taught the basics of SQL and PostgreSQL RDBMS and then taught how to query a relational database. One learns how to write and execute SQL commands, in both a learning environment and in a real-world environment.

This course is described as popular because over 352,000 students have completed it, with 94,725 of them giving it a rating of 4.7 out of 5. It has 12 sections to be completed in 83 lectures.

The estimated time to complete the entire course is approximately 9 hours, with the lecture videos adding up to 9 hours.

Other course resources are 14 articles and 13 downloadable resources. Course completion is confirmed with a certificate of completion.

Moreover, one has lifetime access to the aforementioned course contents and resources. The last update made to this course was in October 2020.

This is the best SQL course for beginners in this review, and it is recommended for everyone.

Key aspects of this course are explained below.
  • Target Audience: Beginners in SQL and SQL-supported RDBMS.
  • Rating: 4.7 following 94,725 ratings.
  • Course Type: Tutorials.
  • Language: English with videos featuring auto-generated French, English, Spanish, Portuguese, Indonesian, Italian, Polish, and German subtitles.

The Tutor

Jose Portilla is a programmer and data scientist who heads the Data Science department in Pierian Data, Incorporated.

Requirements

  • Internet-connected Personal Computer (PC).
  • Installation of PgAdmin and PostgreSQL.

Contents

The key topics covered in the course include the following:
  • PgAdmin and PostgreSQL.
  • SQL statements.
  • GROUP BY statements.
  • JOINS for joining tables.
  • Advanced SQL commands.
  • Creation of Tables and Databases.
  • Conditional Expressions.
  • Procedures.
  • Python with PostgreSQL.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

2. Ultimate MySQL Bootcamp – Go from SQL Beginner to Expert

The Ultimate MySQL Bootcamp

This is a comprehensive SQL course designed for beginners who want to master SQL and use it to generate reports, operate complex databases, and provide data-driven advice to enterprises.

This course is much longer than the afore-reviewed course, but it covers equally well the basics of SQL and shows the learner how to compose complex SQL queries that can be executed to retrieve, add, or update data across multiple tables.

Moreover, this course requires the student to use MySQL and Node.JS to build a functioning web app. As expected, this course uses MySQL as the RDBMS.

Like the course above, this course teaches the learner how to write and execute SQL commands, in both learning and real-world environments.

This course can also be described as popular because over 232,800 students have completed it, with 52,045 of them giving it a rating of 4.6 out of 5.

It has 18 sections to be completed in 322 lectures. The estimated time to complete the entire course is approximately 21 hours, with the lecture videos adding up to 20 hours.

Other course resources are 141 articles and 4 downloadable resources. Course completion is confirmed with a certificate of completion.

Moreover, one has lifetime access to the aforementioned course contents and resources. The last update made to this course was in February 2021.

Key aspects of this course are explained below.
  • Target Audience: Beginners in SQL and SQL-supported RDBMS.
  • Rating: 4.6 following 52,045 ratings.
  • Course Type: Tutorials.
  • Language: English with videos featuring auto-generated French, Romanian, English, Spanish, Portuguese, Indonesian, Italian, Japanese, Polish, and German subtitles.

The Tutor

This course has two instructors – Ian Schoonover and Colt Steele. Ian Schoonover is a full-stack app developer, and Colt Steele is a web developer.

Requirements

  • Internet-connected Personal Computer.
  • Installation of MySQL.

Contents

The key topics covered in the course include the following:
  • MySQL.
  • SQL statements.
  • Data types.
  • Aggregate functions.
  • GROUP BY statements.
  • JOINS for joining tables.
  • CRUD commands.
  • Advanced SQL commands.
  • Creation of Tables and Databases.
  • Conditional Expressions.
  • Procedures.
  • Logical Operators

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

3. BEST FOR DATA VISUALS: Complete Bootcamp for SQL and Data Visualization

SQL and Data Visualization

This is a beginner SQL course designed for students who want to use SQL for data visualization. It uses PgAdmin to create a database, PostgreSQL as the RDBMS, Heroku to host the database, and Metabase as the data visualization tool.

Apart from the fundamentals of SQL, the student learns about data analysis, data visualization, and business intelligence.

Like the 2 courses reviewed above, this course teaches the learner how to write and execute SQL commands in both learning and real-world environments.

The estimated time to complete the entire course is approximately 6 hours, with the lecture videos adding up to 5.5 hours.

It has 18 sections to be completed in 322 lectures. Other course resources are 2 downloadable resources. Course completion is confirmed with a certificate of completion.

Moreover, one has lifetime access to the aforementioned course contents and resources. The last update made to this course was in May 2020.

Over 470 students have completed it, with 74 of them giving it a rating of 4.4 out of 5.

Key aspects of this course are explained below.
  • Target Audience: Beginners in SQL and SQL-supported RDBMS.
  • Rating: 4.4 following 74 ratings.
  • Course Type: Tutorials.
  • Language: English.

The Tutor

Raffi Sarkissian is a data scientist with experience in using data to drive business decisions.

Requirements

  • Internet-connected PC.
  • Installation of PgAdmin and PostgreSQL.

Contents

The key topics covered in the course include the following:
  • PgAdmin and PostgreSQL.
  • SQL statements.
  • Data types.
  • GROUP BY statements.
  • JOINS for joining tables.
  • Advanced SQL commands.
  • Creation of Tables and Databases.
  • Heroku.
  • Conditional Expressions.
  • Procedures.
  • Logical Operators.
  • Data visualization with Metabase.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

4. Complete Developer’s Guide using SQL and PostgreSQL

SQL and PostgreSQL: The Complete Developer's Guide

This is a comprehensive SQL course designed for beginners who want to master SQL and use it to build and design databases that are efficient and easy to work with.

It covers the basics of SQL, database terminology, database design, and how PostgreSQL operates to store data in the hardware layer of the database.

As expected, the learner is taught how to compose complex SQL queries that can be executed to retrieve, add, or update data across multiple tables.

Additionally, the learner is taught about complex concurrency and race conditions, as well as how to use an application programming interface (API) to connect a web-based app to PostgreSQL.

Moreover, the student is taught how to develop common app features including mention and like systems.

Over 10,100 students have completed it, with 1,120 of them giving it a rating of 4.7 out of 5. It has 37 sections to be completed in 289 lectures.

The estimated time to complete the entire course is approximately 23 hours, with the lecture videos adding up to 22 hours. Other course resources are 9 articles and 46 downloadable resources.

There are also 24 coding exercises. Course completion is confirmed with a certificate of completion. Moreover, one has lifetime access to the aforementioned course contents and resources.

The last update made to this course was in February 2021.

Key aspects of this course are explained below.
  • Target Audience: Beginners in SQL and SQL-supported RDBMS.
  • Rating: 4.7 following 1,120 ratings.
  • Course Type: Tutorials and coding exercises.
  • Language: English with videos featuring auto-generated English subtitles.

The Tutor

Stephen Grider is an engineering architect and software developer.

Requirements

  • Internet-connected PC.
  • Installation of PgAdmin and PostgreSQL.

Contents

The key topics covered in the course include the following:
  • PostgreSQL.
  • SQL statements.
  • Data types.
  • Aggregate functions.
  • GROUP BY statements.
  • JOINS for joining tables.
  • CRUD commands.
  • Advanced SQL commands.
  • Creation of Tables and Databases.
  • Conditional Expressions.
  • Procedures.
  • Logical Operators.
  • Database design.
  • Query tuning.
  • Handling concurrency.
  • Data access pattern.
  • Security around PostgreSQL.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

5. BEST FOR MICROSOFT SQL: Microsoft SQL for Beginners

Microsoft SQL for Beginners

This is a beginner course to T-SQL and Microsoft SQL Server, and anyone can take it. It introduces the learner to the T-SQL programming language and explains its database concepts.

The student taught the basic SQL commands that include SELECT, WHERE, ORDER BY, INNER JOIN, HAVING, OUTER JOIN, and GROUP BY commands.

Moreover, the learner is taught how to compose complex SQL queries that can be executed to retrieve, add, or update data across multiple tables.

Additionally, database design and aggregate functions are covered, alongside database normalization. As expected, this course teaches the learner how to write and execute SQL commands in both learning and real-world environments.

The estimated time to complete the entire course is approximately 4 hours, with the lecture videos adding up to 3.5 hours. It has 7 sections to be completed in 39 lectures. Other course resources are 13 downloadable resources.

Course completion is confirmed with a certificate of completion. Moreover, one has lifetime access to the aforementioned course contents and resources.

The last update made to this course was in December 2020. Over 44,500 students have completed it, with 11,330 of them giving it a rating of 4.6 out of 5.

Key aspects of this course are explained below.
  • Target Audience: Beginners in SQL and SQL-supported RDBMS.
  • Rating: 4.6 following 11,330 ratings.
  • Course Type: Tutorials.
  • Language: English with videos featuring auto-generated French, Romanian, English, Spanish, Portuguese, Indonesian, Italian, Polish, and German subtitles.

The Tutor

Brewster Knowlton is a business intelligence expert with experience of using SQL-based databases in the business environment.

Requirements

  • Internet-connected PC.
  • Installation of Microsoft SQL Server Express.

Contents

The key topics covered in the course include the following:
  • Microsoft SQL Server Express.
  • AdventureWorks Database.
  • Data filtering.
  • Data sorting.
  • Queries.
  • Aggregate functions.
  • Data grouping.
  • Filtering groups.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

Best Intermediate-level SQL Courses

6. BEST FOR INTERMEDIATES: Project-Based SQL Course

Project Based SQL Course: Code like a SQL Programmer

This is a project-based course where the student learns advanced SQL through the completion of SQL projects that require him/her to fetch, update, and add data to a complex database, as well as handle data management using SQL commands.

The SQL project is designed to simulate complex real-world SQL work. Moreover, the student is expected to design a database, hence helping his/her understand how SQL works with RDBMS during database creation, design, and maintenance.

This is the best intermediate-level SQL course in this review. Regarding RDBMS, this course uses Microsoft SQL Server 2017 edition.

The estimated time to complete the entire course is approximately 7 hours, with the lecture videos adding up to 6.5 hours. It has 8 sections to be completed in 41 lectures.

Other course resources are 9 downloadable resources, and there is also a coding exercise. Course completion is confirmed with a certificate of completion.

Moreover, one has lifetime access to the aforementioned course contents and resources.

The last update made to this course was in January 2021. Over 10,800 students have completed it, with 421 of them giving it a rating of 4.6 out of 5.

Key aspects of this course are explained below.
  • Target Audience: Intermediate SQL users who understand the basics of RDBMS.
  • Rating: 4.6 following 421 ratings.
  • Course Type: Tutorials and a coding exercise.
  • Language: English with videos featuring auto-generated English subtitles.

The Tutor

Brandon Brown is a programmer with experience in building data-driven applications.

Requirements

  • Internet-connected PC.
  • Installation of Microsoft SQL Server Express.

Contents

The key topics covered in the course include the following:
  • Microsoft SQL Server.
  • Create Database.
  • Data filtering.
  • Data sorting.
  • Queries.
  • Aggregate functions.
  • SELECT.
  • JOINS.
  • INSERT, UPDATE, DELETE.
  • Stored procedures.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

7. BEST BUSINESS FOCUSED COURSE: SQL and Data Analytics Applications in the Real World

SQL: Data Analytics Applications in the Real World

This is an intermediate-level SQL course designed for students who want to use SQL for data visualization and analysis.

It focuses on data schemas in tabulated SQL-queried databases, relationships among tables using foreign keys, table alteration, creation of virtual tables, complex joins of tables, data manipulation in tables using SQL queries, and column restraints, as well as common table expressions.

It uses 4 case studies during the lectures, along with an additional case study after the last topic has been covered.

The estimated time to complete the entire course is approximately 9 hours, with the lecture videos adding up to 8.5 hours. It has 5 sections to be completed in 22 lectures.

Other course resources are 2 downloadable resources. Course completion is confirmed with a certificate of completion.

Moreover, one has lifetime access to the aforementioned course contents and resources. The last update made to this course was in January 2021.

Over 190 students have completed it, with 34 of them giving it a rating of 4.1 out of 5.

Key aspects of this course are explained below.
  • Target Audience: Experienced SQL users.
  • Rating: 4.1 following 34 ratings.
  • Course Type: Tutorials.
  • Language: English with videos featuring auto-generated English subtitles.

The Tutor

The developer of this course is Data Civilisation, which is a technology-based analytics company that uses SQL, python, and PowerBI for data analytics work.

Requirements

  • Internet-connected PC.
  • Installation of Microsoft SQL Server Express.
  • Comprehension of how to use Microsoft SQL Server
  • Ability to use SQL for clause filtering, categorization, joins, aggregation, data conversion, and stored procedures.
  • Completion of a beginner-level SQL course on data visualization is an advantage.

Contents

The key topics covered in the course include the following:
  • Microsoft SQL Server Express.
  • Data filtering.
  • Data sorting.
  • Queries.
  • Virtual tables.
  • Aggregate functions.
  • Data grouping.
  • Filtering groups.
  • Complex table joins.
  • Common table expressions

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

8. BEST SERVER FOCUSED: SQL Server Performance Tuning – Part 1

SQL Server Performance Tuning Part 1

This is a specialist SQL course that focuses on performance tuning of SQL servers so that they deliver optimum performance.

The student learns about the index types that affect the performance of RDBMS, as well as key factors that affect the performance of the Microsoft SQL Server including wait statistics, fragmentation, virtualization, tempDB configuration, caching, blocking, execution plan, log file allocation, locking, database tuning advisor, and common performance issues.

The learner is expected to use the T-SQL programming language, and write basic SQL commands that include SELECT, WHERE, ORDER BY, INNER JOIN, HAVING, OUTER JOIN, and GROUP BY commands.

Additionally, the student must understand SQL Server Administration.

The estimated time to complete the entire course is approximately 6 hours, with the lecture videos adding up to 6 hours.

It has one section that is completed in 37 lectures. Other course resources are 7 downloadable resources. Course completion is confirmed with a certificate of completion.

Moreover, one has lifetime access to the aforementioned course contents and resources.

The last update made to this course was in March 2020. Over 7,300 students have completed it, with 1,464 of them giving it a rating of 4.5 out of 5.

Key aspects of this course are explained below.
  • Target Audience: SQL users, server administrators, network administrators, and database developers.
  • Rating: 4.5 following 1,464 ratings.
  • Course Type: Tutorials.
  • Language: English with videos featuring auto-generated English subtitles.

The Tutor

Raphael Asghar is a production SQL database administrator with 15 years experience of in managing enterprise databases.

Requirements

  • Internet-connected PC.
  • Installation of Microsoft SQL Server Express.

Contents

The key topics covered in the course include the following:
  • Installation of Windows Server in a Virtual Machine.
  • Microsoft SQL Server Express.
  • SQL performance tuning.
  • Autogrowth settings.
  • Indexes and Indexing.
  • B Tree.
  • Operators.
  • Statistics.
  • Locking.
  • Deadlocks.
  • Blocking.
  • Recompilation.
  • Wait statistics.
  • TempDB.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

Best Advanced SQL Courses

9. BEST FOR EXPERTS: SQL Expert Certification Preparation Course

Advanced SQL : SQL Expert Certification Preparation Course

This advanced certification preparation course is designed for an SQL user who aspires to transition from being an intermediate-level Oracle SQL user to be an expert SQL developer and Database SQL specialist.

It covers advanced SQL concepts that are examined in the SQL expert certification examination.

Among these concepts are Oracle SQL Functions, Analytic SQL Functions, Database Objects, Advanced Subqueries, Data Dictionary Views, Advanced-Data Manipulation, Regular Expressions, Windowing Functions, Advanced Aggregation Techniques, and generation of Dynamic SQL Scripts, as well as creation and usage of Views and Sequences.

There are also lessons in the creation and usage of Indexes and Synonyms. Additionally, the advanced SQL query is covered, and there are assessments and quizzes.

This is the best-advanced SQL course in this review. As expected, it uses Oracle RDBMS.

The estimated time to complete the entire course is approximately 14 hours, with the lecture videos adding up to 13 hours.

It has 19 sections that are completed in 138 lectures. Other course resources are 7 articles and 6 downloadable resources.

Course completion is confirmed with a certificate of completion. Moreover, one has lifetime access to the aforementioned course contents and resources.

The last update made to this course was in February 2021, which makes it an up-to-date advanced Oracle SQL course.

Over 22,500 students have completed it, with 1,962 of them giving it a rating of 4.4 out of 5.

Key aspects of this course are explained below.
  • Target Audience: SQL users, server administrators, and database developers.
  • Rating: 4.4 following 1,962 ratings.
  • Course Type: Tutorials and assignments.
  • Language: English with videos featuring auto-generated Romanian, English, Spanish, Indonesian, Italian, Polish, and Thai subtitles.

The Tutor

This course is developed and delivered by Code Star Academy and Oracle Master Training. Code Star Academy is a software training center that develops and teaches courses in SQL, SQL-PL, SQL Tuning, OOP, and Web Development.

Oracle Master Training is an Oracle Architect and Software Developer who has been engaged in SQL and SQL-PL programming for over 15 years.

Requirements

  • Internet-connected PC.
  • Installation of Oracle.
  • Understanding of basic SQL.
  • Understanding of how Oracle RDBMS works.

Contents

The key topics covered in the course include the following:
  • Installation of Oracle and SQL Developer.
  • Data Manipulation.
  • Analytic Functions.
  • Database Objects.
  • Operators.
  • Data dictionary views.
  • Data transformation.
  • Creation, Usage, and Management of Sequences.
    Indexes.
  • Creation, Usage, and Analysis of Synonyms.
  • Advanced Subqueries.
  • Hierarchical queries.
  • Materialized views.
  • Dynamic SQL scripts.
  • Regular expressions.
  • Advanced SQL functions.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

10. SQL Advanced and Expert Certification Preparation Course

SQL Advanced

This advanced certification preparation course is designed for an SQL user who aspires to be a senior SQL developer.

It covers advanced SQL concepts as it applies to database management, data manipulation, hierarchical queries, CUBE and ROLLUP operators, hierarchical data, and table management through partitions, as well as performance optimization of the RDBMS.

Also, it covers the generation of advanced reports, the use of analytic functions for data analysis, and the use of regular expressions for pattern matching. Additionally, the student is taught the difference between materialized views and views.

In this course, Analytic SQL is used for data modeling, aggregation, analysis, and reporting. Likewise, its lessons are designed to prepare the student to take an SQL expert-level certificate examination. It uses Oracle RDBMS.

The estimated time to complete the entire course is approximately 5 hours, with the lecture videos adding up to 4.5 hours. It has 11 sections that are completed in 82 lectures.

Other course resources are 7 articles and 21 downloadable resources. Course completion is confirmed with a certificate of completion.

Moreover, one has lifetime access to the aforementioned course contents and resources. The last update made to this course was in December 2018. Over 9,600 students have completed it, with 1,335 of them giving it a rating of 4.2 out of 5

Key aspects of this course are explained below.
  • Target Audience: SQL users, server administrators, and database developers.
  • Rating: 4.2 following 1,335 ratings.
  • Course Type: Tutorials.
  • Language: English.

The Tutor

Amarnath Reddy is an Oracle Architect who graduated as a Computer Scientist and has participated in data architecture projects.

Requirements

  • Internet-connected PC.
  • Installation of Oracle.
  • Understanding of basic SQL.

Contents

The key topics covered in the course include the following:
  • Installation of Oracle, SQL Developer, and Java SDK.
  • Data Manipulation.
  • Analytic Functions.
  • Operators.
  • Data transformation.
  • Hierarchical queries.
  • Table partitioning.
  • Extensions to the group.
  • Materialized views.
  • Flashback operations.
  • Regular expressions.

Registration allows one to access course contents via the internet-enabled PC, Smart TV, and smart mobile devices.

An Introduction to SQL Databases

For any website to display information on the (monitor) screen, it needs to fetch the information – generically described as data – from the database (DB).

This means that every website must have a database, and this also applies to any application that stores data input from the user.

The database features a database management system (DBMS) that allows for information to be fetched, changed, or added into the database.

DBMS is part of the database technology that powers modern websites and cloud-enabled apps. The person who manages the database is the database administrator (or database manager), and (s)he needs to use a programming language to store, manipulate, and retrieve data from the database.

Also, this programming language must be easily understood and easy to use.

The high-level programming language used to manage and manipulate data stored in a relational DBMS is called the structured query language or simply SQL.

What is SQL?

Simply put, SQL is a computer language that is used to communicate with a relational database via its database management system. This means that SQL communicates with the DBMS, and this DBMS then executes commands on the database as per the instructions it has received from the SQL information.

Structured Query Language

sql

This high-level computer language is a fastidious domain-specific language that only works with relational DBMS (RDBMS) and relational data stream management systems (RDSMS), and this makes it quite effective for handling structured data.

A domain-specific programming language is simply a language designed to be used with only one application, or a closely related set of applications, where the language works on a targeted subject in the application.

For SQL, the application is the relational DBMS or RDSMS. SQL is a fourth-generation language and is regarded as a set-based declarative language. In the RDSMS, SQL is used for stream processing.

A short history of SQL

SQL is the successor of SEQUEL (abbreviation for Structured English Query Language), which was used in System R DBMS that was run by IBM in San Jose in the 1970s-80s.

Relational Software Incorporated, (which later became Oracle Corporation) also developed a SQL-based domain-specific language that was released as Oracle Version 2, or Oracle V2, in 1979.

Later, a standard language definition for managing and manipulating data using the relational model described by Edgar Codd in 1970 was adopted.

This standard language definition was called the database language SQL, and it was officially adopted as the standard by American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) in 1986 and 1987 respectively.

The latest version of SQL standards was published in 2019 as SQL:2019.

SQL was developed by Donald Chamberlin and Raymond Boyce in 1974 as SEQUEL. Due to trademark concerns, the name SEQUEL was changed to SQL, and its standards were published by the International Electrotechnical

Commission thus preparing it for its first public release in 1986 as SQL-86 as an open-source, cross-platform RDBMS software.

The latest stable is SQL:2016 which was released in December 2016. A major advantage of SQL over older propriety domain-specific computer languages for DBMS was its elimination of specifying to the DBMS on how to reach the data, i.e, informing the DBMS where the data needed is specifically stored in the database. Instead, SQL specifies what needs to be done in the database.

Working with SQL

Modification can be made on SQL codebase and this modifies its standards thus allowing for the creation of a new subset of SQL standards.

Currently, there are several standard subsets such as the ANSI SQL, SQL2/SQL92, and SQL3/SQL99. Database vendors can support specific subsets of standards.

Relational Database

In SQL, data is stored in a table. This table has two attributes, which are its columns and rows. The table needs to be assigned a table name, and each column is assigned a column name that serves as an attribute in the table. Each column is made up of a set of rows or tuples.

The table name and its associated attributes (column names) form the schema of the table. If the attribute has a known specific value, then it is described as a key, and it is underlined to differentiate it from other attributes.

The table name is also described as the relation, and this allows for an SQL command to be composed and executed. It is for this reason that the database that holds this table is called a relational database.

The SQL table is flat because it can only hold atomic data types, mainly integers, and characters. The tuple contains a record that can be modified or deleted using SQL commands.

The basic syntax of the SQL command is as follows:

SELECT (attribute[s]) FROM (relation[s]) WHERE (conditions), for example (e.g) SELECT column_name FROM table_name WHERE value>x.

This command allows one to query a table for specific data and then retrieve it. Its syntax allows for the command to be case insensitive, except for characters in single quotes, e.g SELECT or select will work, but ‘SELECT’ and ‘select’ are regarded as different atomic character data.

There are 3 data types in the SQL standard: predefined data type, constructed type, and user-defined type. The atomic data types are part of the predefined data type.

Syntax, Procedural Extension, and Sub-Languages

SQL is static and strongly typed computer language whose files carry the filename extension .SQL.

It has 4 sub-languages – the data manipulation language, data query language, data control language, and the data definition language.

Its syntax has language elements, and its procedural extensions give it the functionality of a procedural programming language.

The main procedural extensions are:
  • Procedural SQL (PSQL), SQL Procedural Language (SQL-PL)
  • Stored Procedural Language (SPL)
  • SQL Persistent Store Modules (SQL/PSM)
  • Invantive PSQL,
  • Starkey Stored Procedures (SSP),
  • SQLScript,
  • Watcom-SQL
  • Advanced Business Application Programming (ABAP)
  • and Transact SQL (T-SQL).

There are SQL extensions that can give it objected-oriented programming (OOP) functionality, and Java code can also be supported when the SQL/JRT extension is added. SQL/JRT is the SQL Routines and Types for the Java Programming Language, and it allows Java to be stored in SQL procedures.

Additionally, to manage .NET assemblies in the relational DB, the extension used in the SQL Server Common Language Runtime (SQLCLR).

Most importantly, a programmer can write an SQL extension using any of the available programming languages used to develop a database, e.g C, Python, Perl, and Java.

Each sub-language in SQL is made up of a set of different types of statements that are well-purposed to serve particular tasks of database management.

The 4 sub-languages of SQL

  • Data Definition Language (DDL): This is used to create a table and specify its attributes, as well as delete a table or alter a table. It allows for schema creation- including the schema of each relation and its physical storage structure – and schema manipulation
  • Data Manipulation Language (DML): This is used to perform a data query in a table, as well as perform data manipulation in a table using a specific command like delete, insert, and update. This allows for a change of data in the tuples.
  • Data Query Language (DQL): It is used to perform queries for specific data in a schema, or schema objects. An example of DQL is the SELECT SQL command.
  • Data Control Language (DCL): This is the language used for data access control and authorization of users to access specific tables in the database. Its two main SQL commands are GRANT (for giving a user access to a particular table to perform a task) and REVOKE (for denying the user access to a table in a database).

SQL Syntax

In SQL, the command to the DBMS is issued as a statement. This statement has multiple language elements. The main language elements are:

  • Clause: The constituent component of any SQL statement or query. The statement is made up of 2 or more clauses.
  • Expression: This is used to create a table, and insert, delete, or update a scalar value in a tuple, as well as insert or delete a column or a row.
  • Predicate: This is used to specify a condition to be evaluated to the SQL Boolean truth values or three-valued logic (3VL), thus allow for a change in program flow or limit the effect of an SQL query or statement.
  • Query: This is an SQL command that uses a specific criterion to retrieve data from the database.
  • Statement: This is the SQL command that creates a persistent effect on the schema and the data in it, as well as controls program flow, sessions, connections, diagnostics, and transactions. The statement terminator is usually a semicolon.
  • Whitespace: This is insignificant in the command because it is ignored during code execution, but it serves to make the SQL code format-able and readable.

SQL standards specify the syntax used, and because there are different sets of SQL sub-standards, there exist different specifications of SQL syntax.

Usually, database vendors modify the SQL standard to conform to their database systems, hence giving rise to propriety SQLs that differ from the standard (basic) SQL. Usually, a proprietary SQL is designed to deliver optimum performance on a specific database system.

References

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