Search results
Results from the WOW.Com Content Network
In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. This can have major impact on performance because the correlated subquery might get recomputed every time for each row of the outer query is processed.
Recursive CTEs are also supported by Microsoft SQL Server (since SQL Server 2008 R2), [2] Firebird 2.1, [3] PostgreSQL 8.4+, [4] SQLite 3.8.3+, [5] IBM Informix version 11.50+, CUBRID, MariaDB 10.2+ and MySQL 8.0.1+. [6] Tableau has documentation describing how CTEs can be used. TIBCO Spotfire does not support CTEs, while Oracle 11g Release 2's ...
A subquery can use values from the outer query, in which case it is known as a correlated subquery. Since 1999 the SQL standard allows WITH clauses, i.e. named subqueries often called common table expressions (named and designed after the IBM DB2 version 2 implementation; Oracle calls these subquery factoring).
Starting from Oracle database 11g, iSqlplus (web based) and sqlplus GUI no longer ship with Oracle database software. [7] The command-line SQL Plus interface continues in use, mostly [ citation needed ] for non-interactive scripting or for administrative purposes.
Oracle Database is available by several service providers on-premises, on-cloud, or as a hybrid cloud installation. It may be run on third party servers as well as on Oracle hardware (Exadata on-premises, on Oracle Cloud or at Cloud at Customer). [5] Oracle Database uses SQL for database updating and retrieval. [6]
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
SQLite: A VIEW named "dual" that works the same as the Oracle "dual" table can be created as follows: CREATE VIEW dual AS SELECT 'x' AS dummy; SAP HANA has a table called DUMMY that works the same as the Oracle "dual" table. Teradata database does not require a dummy table. Queries like 'select 1 + 1' can be run without a "from" clause/table name.
Conversely, an inner join can result in disastrously slow performance or even a server crash when used in a large volume query in combination with database functions in an SQL Where clause. [2] [3] [4] A function in an SQL Where clause can result in the database ignoring relatively compact table indexes. The database may read and inner join the ...