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Previous Page: sort the data in the reverse order, select only the first {rows} rows, where the {unique_key} is less than {first_val} (the value of the {unique_key} of the first row in the current page), and sort the result in the correct order; Read and send to display all the rows read from the database
PL/SQL refers to a class as an "Abstract Data Type" (ADT) or "User Defined Type" (UDT), and defines it as an Oracle SQL data-type as opposed to a PL/SQL user-defined type, allowing its use in both the Oracle SQL Engine and the Oracle PL/SQL engine. The constructor and methods of an Abstract Data Type are written in PL/SQL.
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.
The first version of SQL Plus was called UFI ("User Friendly Interface"). UFI appeared in Oracle database releases up to Version 4. After Oracle programmers had added new features to UFI, its name became Advanced UFI. The name "Advanced UFI" changed to "SQL Plus" with the release of the version 5 of Oracle. [2]
Indexes are useful for many applications but come with some limitations. Consider the following SQL statement: SELECT first_name FROM people WHERE last_name = 'Smith';. To process this statement without an index the database software must look at the last_name column on every row in the table (this is known as a full table scan).
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.
The cost is predictable, as every time database system needs to scan full table row by row. When table is less than 2 percent of database block buffer, the full scan table is quicker. Cons: Full table scan occurs when there is no index or index is not being used by SQL. And the result of full scan table is usually slower that index table scan.
Oracle SQL Developer versions [11] Version Release Date Description Releases prior to 1.0 Prior to version 1.0, Oracle Corporation labeled the product "Raptor" 1.0 March 2006 The first release 1.1 December 2006 1.2.1 August 2007 1.5 April 2008 1.5.1 June 2008 1.5.3 December 2008 1.5.4 March 2009 1.5.5 July 2009 2.1 RC1 December 2009 2.1 Patch 1