Hint (SQL)

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In various SQL implementations, a hint is an addition to the SQL standard that instructs the database engine on how to execute the query. For example, a hint may tell the engine to use or not to use an index (even if the query optimizer would decide otherwise).

Contents

Implementation

Different database engines use different approaches in implementing hints.

See also

Related Research Articles

MySQL SQL database engine software

MySQL is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter, and "SQL", the abbreviation for Structured Query Language. A relational database organizes data into one or more data tables in which data types may be related to each other; these relations help structure the data. SQL is a language programmers use to create, modify and extract data from the relational database, as well as control user access to the database. In addition to relational databases and SQL, an RDBMS like MySQL works with an operating system to implement a relational database in a computer's storage system, manages users, allows for network access and facilitates testing database integrity and creation of backups.

PostgreSQL Free and open-source relational database management system

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SQL is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). It is particularly useful in handling structured data, i.e. data incorporating relations among entities and variables.

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EnterpriseDB American software company

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SQL:2011 or ISO/IEC 9075:2011 is the seventh revision of the ISO (1987) and ANSI (1986) standard for the SQL database query language. It was formally adopted in December 2011. The standard consists of 9 parts which are described in detail in SQL. The next version is SQL:2016.

References

  1. MySQL 5.5 Reference Manual: 12.2.9.3 Index Hint Syntax
  2. Mike Ault: Oracle SQL Hints Tuning
  3. Postgres Plus Advanced Server Performance and Scalability Guide: Query Optimization Hints
  4. "Postgres Plus Advanced Server Oracle Compatibility Developer's Guide: Optimizer Hints". Archived from the original on 2014-04-19. Retrieved 2013-06-24.
  5. MSSQL 2017 Documentation