The Tool Desk
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What SQL is used for
SQL lets people and software express operations on a relational database: creating or changing database structures, adding or updating data, and retrieving information. A database commonly organizes information in tables made up of rows and columns.
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For example, this illustrative query requests the name column from a table named customers:
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SELECT name FROM customers;The example demonstrates the basic purpose of a query; SQL syntax and supported features can vary between database products. Also, unless a query specifies sorting, the order of returned rows is not guaranteed, as PostgreSQL’s tutorial explains in its SQL tutorial.
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SQL is a standard, not a particular database product
ISO/IEC 9075 is the formal standard for Database Language SQL. PostgreSQL’s conformance documentation identifies the 2023 edition as ISO/IEC 9075:2023, also called SQL:2023. PostgreSQL, MySQL, and SQL Server are database products; SQL is the language they implement to varying degrees.
The existence of a standard does not mean every database accepts identical syntax or supports every feature. Products implement different subsets and may add extensions. PostgreSQL’s SQL conformance documentation describes its own implementation, including features that extend beyond the standard. For work across systems, check the specific feature and syntax in each product’s documentation rather than assuming it will transfer unchanged.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Where the name came from
According to PostgreSQL’s archived historical account, Donald Chamberlin and colleagues at IBM Research defined SEQUEL, short for Structured English Query Language, in 1974. The account says a later revision was renamed SQL; ANSI ratified an SQL standard in 1986, and ISO accepted one in 1987. These dates are reported by that historical documentation, not an IBM archival source. See the PostgreSQL 6.5 history chapter.
Quick Recap
What to remember
- SQL means Structured Query Language.
- It is used to define database structures and add, change, and retrieve data.
- It is standardized for relational databases, but individual products can differ in supported features and syntax.
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