What Is SQL: Common Uses and Defining Features

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Data query language (DQL) consists of instructions for retrieving data stored in relational databases. Software applications use the SELECT command to filter and return specific results from a SQL table. SQL is, fundamentally, a programming language designed for accessing, modifying and extracting information from relational databases. As a programming language, SQL has commands and a syntax for issuing those commands. Structured Query Language (SQL) is a standardized programming language that is used to manage relational databases and perform various operations on the data in them.

SQL has quite a few inconsistencies and also some special rules to prevent you from constructing SQL statements that look perfectly legal but that don’t make sense. A cyberattack known as SQL injection involves tricking the database with SQL queries. To retrieve, alter, or corrupt data in a SQL database, hackers use SQL injection. To execute a SQL injection attack, for instance, they might enter a SQL query in place of a person’s name in a submission form. In common usage, SQL encompasses DDL and DML commands for CREATE, UPDATE, modified, or other operations on database structure.

Where to Learn SQL

The following SQL query will insert data into the records in the customers table. The relational part means that one table can relate to another table. By adding a customer id column to our orders table, we can relate our order records to our customer records. Every company stores data to some extent, which means having the skills to access and manipulate data can result in a high-paying career.

Based on the needs of the business, database engineers create and modify database objects using DDL. The CREATE command, for instance, is used by the database engineer to create database objects like tables, views, and indexes. Microsoft’s relational database management system, which uses SQL to manipulate data, is formally known as SQL Server. There are various editions of the MS SQL Server, and each is tailored for particular workloads and requirements. Structured Query Language is a computer language that we use to interact with a relational database.

Interoperability and standardization

For example, Microsoft offers a set of extensions called Transact-SQL, while Oracle’s extended version of the standard is Procedural Language for SQL. Commercial vendors offer proprietary extensions to differentiate their product offerings by giving customers additional features and functions. As a result, the different variants of extended SQL offered by vendors are not fully compatible with one another.

what is SQL

SQL standards are a set of formally defined guidelines of the structured query language (SQL). The American National Standards Institute (ANSI) and International Organization for Standardization (ISO) adopted the SQL standards in 1986. Software vendors use the ANSI SQL standards to build SQL database software for developers. Database administrators use data control language (DCL) to manage or authorize database access for other users. For example, they can use the GRANT command to permit certain applications to manipulate one or more tables. By looking at the job postings, we can see an enormous demand for SQL Developers across the globe.


Data definition language (DDL) refers to SQL commands that design the database structure. Database engineers use DDL to create and modify database objects based on the business requirements. For example, the database engineer uses the CREATE command to create database objects such as tables, views, and indexes.

You can use SQL to adjust the information present in a database to be more accurate and up-to-date. The commands to do so are relatively simple (“UPDATE” and “DELETE” illustrate https://www.globalcloudteam.com/ this) which makes the process of changing existing data relatively easy and straightforward. ISO/IEC 9075 is complemented by ISO/IEC SQL Multimedia and Application Packages.

SQL Constraints

The relational engine uses transaction control language (TCL) to automatically make database changes. For example, the database uses the ROLLBACK command to undo an erroneous transaction. The storage engine, or database engine, is the software component that processes the byte code and runs the intended SQL statement. It reads and stores the data in the database files on physical disk storage.

  • This makes it necessary for a programmer to learn SQL markup before they can use it effectively.
  • The idea of the relational database was introduced back in 1970 by Edgar Frank (Ted) Codd, an English computer scientist at IBM.
  • The relational part means that one table can relate to another table.
  • The system stores multiple database tables that relate to each other.
  • Not all SQL-on-Hadoop tools support all of the functionality offered in relational implementations of SQL.

The parser verifies that the SQL statement conforms to SQL semantics, or rules, that ensure the correctness of the query statement. For example, the parser checks if the SQL command ends with a semi-colon. While you can gain proficiency in SQL via a coding bootcamp, such programs when to use NoSQL vs SQL don’t typically offer certification. Your best bet will be to acquire your fundamental understanding of SQL via a bootcamp or self-guided courses, then study for one of the exams linked below. A FULL JOIN returns rows if it identifies a match in one of the tables.


Allen G. Taylor is a 30-year veteran of the computer industry and the author of over 40 books, including SQL For Dummies and Crystal Reports For Dummies. He lectures nationally on databases, innovation, and entrepreneurship. He also teaches database development internationally through a leading online education provider. In addition to MySQL, there are several other open-source SQL database management systems, including PostgreSQL, Ingres and Firebird.

what is SQL

Relational databases use byte code to efficiently perform database searches and modifications. Structured query language (SQL) implementation involves a server machine that processes the database queries and returns the results. The SQL process goes through several software components, including the following. SQL commands used to create the database structure are known as data definition language (DDL).

SQL Injection

With SQL, you can store, manipulate, and retrieve data from relational databases. SQL queries and other operations take the form of commands written as statements and are aggregated into programs that enable users to add, modify or retrieve data from database tables. NoSQL refers to non-relational databases that don’t use tables to store data. Developers store information in different types of NoSQL databases, including graphs, documents, and key-values. NoSQL databases are popular for modern applications because they are horizontally scalable. Horizontal scaling means increasing the processing power by adding more computers that run NoSQL software.

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