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MEMORY is designed to store data that must be accessed quickly, for example caches, or intermediate data that needs to be transformed before storing it to regular tables. In MariaDB and before MySQL 5.6, MEMORY was used for internal temporary tables, e.g. to materialize the intermediate results of a query.
Memory retrieval time and the complexity of memory requirements can increase application operation time and system complexity relative to what would be required by straight formula computation. The possibility of polluting the cache may also become a problem.
In SQL Server 2012, an in-memory technology called xVelocity column-store indexes targeted for data-warehouse workloads. Mimer SQL: Mimer Information Technology SQL, ODBC, JDBC, ADO.NET, Embedded SQL, C, C++, Python Proprietary Mimer SQL is a general purpose relational database server that can be configured to run fully in-memory.
For example, if an internal node has 3 child nodes (or subtrees) then it must have 2 keys: a 1 and a 2. All values in the leftmost subtree will be less than a 1 , all values in the middle subtree will be between a 1 and a 2 , and all values in the rightmost subtree will be greater than a 2 .
Query plans for nested SQL queries can also be chosen using the same dynamic programming algorithm as used for join ordering, but this can lead to an enormous escalation in query optimization time. So some database management systems use an alternative rule-based approach that uses a query graph model. [7]
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
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Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.