SQL standards refer to the set of guidelines and rules that define how SQL (Structured Query Language) should be written and executed across different database systems. These standards aim to ensure consistency and compatibility, so that SQL queries can work across various databases.

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1. SQL-86 (First SQL Standard)

The first formal SQL standard was introduced by in 1986. It provided basic guidelines for query language features like SELECT, INSERT, UPDATE, and DELETE, and set the foundation for later versions.

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2. SQL-92 (ANSI SQL-92)

SQL-92 is one of the most significant updates to the SQL standard, adding more advanced features like:
  • JOIN operations (inner, outer, left, right)
  • Subqueries (nested queries)
  • Aggregate functions (SUM, COUNT, AVG, etc.)
  • Data types like CHAR, VARCHAR, INT, DATE, etc.
  • Improved NULL handling (IS NULL)
This version made SQL much more powerful and widely adopted across different database systems.

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3. SQL:1999 (SQL-99)

This update introduced features like:
  • Triggers (to automatically respond to events in the database)
  • Recursive queries (using the WITH clause for complex queries)
  • Object-oriented SQL (support for object-relational database systems)
  • Common Table Expressions (CTEs) for better readability of complex queries
SQL:1999 further extended SQL’s capabilities to handle more advanced tasks.

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4. SQL:2003

Introduced important additions, including:
  • XML support (ability to handle XML data types within SQL queries)
  • Window functions (such as ROW_NUMBER(), RANK(), etc., for complex data analysis)
  • MERGE statement (for performing INSERT, UPDATE, or DELETE operations in a single query)
SQL:2003 improved SQL’s ability to deal with structured and semi-structured data.

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5. SQL:2008

SQL:2008 included improvements like:
  • Enhanced join capabilities
  • Table expressions
  • Improvements for handling multiple result sets in queries

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6. SQL:2011

This version focused on:
  • Temporal tables (handling of time-based data and changes over time)
  • Enhancements to window functions
  • More robust support for recursive queries

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7. SQL:2016

  • JSON support (handling JSON data similar to XML in SQL queries)
  • Enhanced features related to period temporal tables and introduced polymorphic table functions.
  • Improvements to row-level security and search capabilities

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8. SQL:2019

  • Further enhancements in JSON handling and integration of Python routines within SQL. - Advanced sharding capabilities to improve scalability.