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In a database, a view is the result set of a stored query that presents a limited perspective of the database to a user. [1] This pre-established query command is kept in the data dictionary.
A common table expression, or CTE, (in SQL) is a temporary named result set, derived from a simple query and defined within the execution scope of a SELECT, INSERT, UPDATE, or DELETE statement. CTEs can be thought of as alternatives to derived tables ( subquery ), views , and inline user-defined functions.
PostgreSQL and some other databases have support for foreign schemas, which is the ability to import schemas from other servers as defined in ISO/IEC 9075-9 (published as part of SQL:2008). This appears like any other schema in the database according to the SQL specification while accessing data stored either in a different database or a ...
PostgreSQL claims high, but not complete, conformance with the latest SQL standard ("as of the version 17 release in September 2024, PostgreSQL conforms to at least 170 of the 177 mandatory features for SQL:2023 Core conformance", and no other databases fully conformed to it [79]). One exception is the handling of unquoted identifiers like ...
A database trigger is procedural code that is automatically executed in response to certain events on a particular table or view in a database.The trigger is mostly used for maintaining the integrity of the information on the database.
Isolation is typically enforced at the database level. However, various client-side systems can also be used. It can be controlled in application frameworks or runtime containers such as J2EE Entity Beans [2] On older systems, it may be implemented systemically (by the application developers), for example through the use of temporary tables.
Cursors allocate resources on the server, such as locks, packages, processes, and temporary storage. For example, Microsoft SQL Server implements cursors by creating a temporary table and populating it with the query's result set.
Without this named pipe one would need to write out the entire uncompressed version of file.gz before loading it into MySQL. Writing the temporary file is both time-consuming and results in more I/O and less free space on the hard drive. PostgreSQL's command line utility, psql, also supports loading data from named pipes. [4]