SQL
abbreviation
SQL is a language for querying and managing data in a relational database and defining that database's structure.
The application uses SQL to retrieve all outstanding orders for a customer.
SQL is commonly expanded as Structured Query Language. Developers and applications use it to give instructions to a relational Glossary · In briefdatabaseA database is a structured collection of data that software can store, retrieve and modify. A database management system controls access to that data.Read more. It retrieves, adds, updates or deletes data and also defines tables, columns and relationships.
How does an SQL command work?
An SQL command describes the required result. SELECT retrieves data from one or more tables, for example. Conditions determine which rows qualify, while sorting and grouping determine how the database assembles the result. Such an instruction is also called a Glossary · In briefqueryA query is a targeted instruction to a system to retrieve, filter, combine or modify data.Read more.
Other commands change the database's contents or structure. INSERT adds data, UPDATE changes it and DELETE removes it. Commands such as CREATE TABLE define parts of the Glossary · In briefdata modelA data model describes which data a system records, how that data is related and which rules it must satisfy.Read more. The database system decides how to execute the instruction, using available indexes among other information.
Is SQL the same in every database?
SQL is standardized, but each database system uses its own dialect. PostgreSQL, MySQL and Microsoft SQL Server support the same fundamentals but differ in functions, data types and additional syntax. A simple query often works in several systems, while a complex one may need changes.
SQL is also different from a database program. PostgreSQL is a database system that understands SQL. SQL itself is the language used to give it instructions. An Glossary · In briefORMAn ORM is software that maps objects in program code to tables and relationships in a relational database. ORM stands for Object-Relational Mapping.Read more can construct many of those instructions from application code, but usually still uses SQL underneath.