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The TRUNCATE TABLE mytable statement is logically (though not physically) equivalent to the DELETE FROM mytable statement (without a WHERE clause). The following characteristics distinguish TRUNCATE TABLE from DELETE: In the Oracle Database, TRUNCATE is implicitly preceded and followed by a commit operation. (This may also be the case in MySQL ...
Though database systems use SQL, they also have their own additional proprietary extensions that are usually only used on their system. For example, Microsoft SQL server uses Transact-SQL (T-SQL), which is an extension of SQL. Similarly, Oracle uses PL-SQL, which an Oracle-specific SQL extension.
A derived table is the use of referencing an SQL subquery in a FROM clause. Essentially, the derived table is a subquery that can be selected from or joined to. The derived table functionality allows the user to reference the subquery as a table. The derived table is sometimes referred to as an inline view or a subselect.
The DROP statement destroys an existing database, table, index, or view. A DROP statement in SQL removes a component from a relational database management system (RDBMS). The types of objects that can be dropped depends on which RDBMS is being used, but most support the dropping of tables, users, and databases.
Query by Example (QBE) is a database query language for relational databases. It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL . [ 1 ] It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions.
Some database implementations adopted the term upsert (a portmanteau of update and insert) to a database statement, or combination of statements, that inserts a record to a table in a database if the record does not exist or, if the record already exists, updates the existing record.
Suppose there is a simple database that lists people and addresses. More than one person can live at a particular address and a person can live at more than one address (this is an example of a many-to-many relationship). The database only has three tables, person, address, and pa, with the following data:
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.