What is SQL (structured query language)?

At a glance

• Declarative language: SQL describes what should be queried—not how the database executes the query.
• Enables access to structured data through commands such as SELECT, INSERT, UPDATE, and DELETE.
• Forms the basis for data analysis, reporting, and data warehouse processes.
• Supported by all leading relational database systems: MySQL, PostgreSQL, SQL Server, SAP HANA.

SQL definition

The abbreviation SQL stands for structured query language and refers to a standardized, internationally recognized query language for managing and processing data in relational database systems.

SQL can be used to create, modify, manage, and query databases. Typical applications include inserting new data, updating existing records, and deleting data that is no longer required. SQL can also be used to create complex queries for selectively filtering and analyzing information.

As a declarative language, SQL describes what a user wants to achieve—for example, which data is required—without specifying exactly how the database should perform the task. This makes SQL a key tool for business intelligence, data warehousing, and many applications involving large volumes of data and modern data analysis.

How does SQL work?

SQL processes database queries in several steps to ensure that data is stored, retrieved, or modified correctly, securely, and efficiently. Various components work closely together:

• Parser (syntax and access checks) Checks whether the user executing the query has the necessary permissions to perform the requested operation. Breaks the SQL statement down into individual elements (“tokenization”) and checks whether the syntax complies with the applicable rules.
• Relational engine (query optimization) Converts the validated statement into so-called bytecode. Creates an execution plan to read or modify data as efficiently as possible. Optimizes recurring queries and selects the fastest access method.
• Storage engine (physical data execution) Executes the execution plan: it reads data from disk or writes new information to the database. Permanently stores changes and returns the results to the requesting application.

What are the most important SQL commands?

There are various SQL commands for managing data in relational databases. Some of the most important include:

Data access and manipulation (DML)

• SELECT: Query data from one or more tables, e.g.: SELECT Name FROM Suppliers WHERE City = ‘Hamburg’
• INSERT: Insert new records into a table, e.g.: INSERT INTO Suppliers (Name, City) VALUES (‘Max Mustermann’, ‘Hamburg’)
• UPDATE: Modify existing records, e.g.: UPDATE Suppliers SET PhoneNumber = ‘new phone number’ WHERE Name = ‘Max Mustermann’
• DELETE: Delete records from a table, e.g.: DELETE FROM Suppliers WHERE City = ‘Leipzig’

Database structure (DDL)

• CREATE: Create new database objects, such as tables.
• ALTER TABLE: Modify the structure of database objects, e.g.: ALTER TABLE Suppliers ADD COLUMN ContractEnd DATE
• DROP: Delete database objects, e.g.: DROP TABLE Suppliers_Old

Access control (DCL)

• GRANT: Grant user permissions.
• REVOKE: Revoke user permissions.

Joining data

• JOIN: Combine data from multiple tables.

What are the advantages of SQL?

SQL is virtually indispensable when working with relational databases. Key advantages include:

What is the difference between SQL and MySQL?

SQL and MySQL have different roles in the world of databases: SQL is the language, while MySQL is a specific database management system.

• SQL is the standardized language for managing and querying relational databases. It defines how databases are structured and how data is processed, regardless of which software is used.
• MySQL is a widely used relational database management system (RDBMS) that uses SQL commands to store, manage, and provide data. MySQL is open source, developed by Oracle, and can be installed on various operating systems or deployed in the cloud.
• Language vs. system: SQL is a syntax and set of rules; MySQL is software that implements those rules.
• Alternative systems: In addition to MySQL, other database systems use SQL, such as Microsoft SQL Server and PostgreSQL.

The difference between SQL and MySQL is therefore that SQL describes how databases are accessed, while MySQL is one of many software solutions that use SQL as a query language.

Use cases: Where is SQL used in controlling?

SQL forms the technical basis for handling structured data in controlling and business intelligence. The following examples show concrete areas of application.

Summary

SQL is an indispensable foundation of modern data management and analysis. As a standardized, cross-platform language, it enables consistent, fast, and secure database operations—from simple queries to complex analyses in data warehouse architectures. Bissantz uses SQL as the technical foundation of DeltaMaster while ensuring that the complexity remains in the background: business users receive clear analyses and comprehensible visualizations without having to write a single line of SQL themselves.