Solution Guide for Migrating Oracle on UNIX to SQL Server - Willy .Net

126 Developing: Databases — <strong>Migrating</strong> Schemas To create a view using T-SQL, use the following syntax:Table 6.23 offers a comparison of the CREATE VIEW statements in <strong>Oracle</strong> andSQL Server.Table 6.23: SQL Statement <strong>for</strong> Creating Views in <strong>Oracle</strong> and SQL Server<strong>Oracle</strong>CREATE [OR REPLACE] [FORCE |NO FORCE] VIEW [schema.]view_nameSQL ServerCREATE VIEW [owner.]view_namename [,…] ) ][ ( column_[ ( column_alias [ inline_constraint ] [,…] [, AS select_statementout_of_line_constraint ] ) ]AS select_statement[ WITH READ ONLY ][ [ WITH CHECK OPTION ] [CONSTRAINT constraint_name ] ][ WITH CHECK OPTION ]In O racle, views can be created without permissions on the base objects, or even withoutthe base objects existing, by using the FORCE keyword. This is not allowed inSQL Server. SQL Server also does not allow ORDER BY and GROUP BY clauses in theview definition.Note When a view is created in <strong>Oracle</strong> using an asterisk (*) in the SELECT clause, theasterisk is expanded to the actual column names in the definition of the view.SQ L Server retains the exact definition used in the DDL. <strong>Oracle</strong> does the same thingwhen an asterisk (*) is not used. While converting from <strong>Oracle</strong> to SQL Server, the viewdefinition may be changed back to an asterisk instead of specifying every column.Stored ProgramsOra cle and SQL Server have the capability to store complex business logic (beyondconstraints) inside the database. The code to support such requirements cannot beprovided by SQL because it cannot execute commands based on logical conditions. Italso fails to support looping operations. In spite of recent extensions to SQL, such asinco rporation of a CASE expression, it is still difficult to per<strong>for</strong>m more than one operationbased on a logical condition using these methods. The need to implement controlstructures and programming constructs cannot be met with SQL alone. Hence <strong>Oracle</strong>and SQL Server both offer procedural extensions to SQL, PL/SQL, and Transact-SQL ( T-SQL), respectively, that offer a more complete environment <strong>for</strong> defining stored programs(or subprograms).Stored programs provide modularity (top-down design), encapsulation (logic is hidden),abstraction (black box approach), security (only execute on subprogram), andextensibility (user-defined functionality). Additionally, existence inside the databasepromotes accessibility (available to all users), reuse (available to all database users),speed of execution (stored programs are in compiled <strong>for</strong>m), per<strong>for</strong>mance (handling oflarge amounts of data close to its source), and reduced resource requirements (reducesnetwork bandwidth, memory, and so on because only the results are transported).In <strong>Oracle</strong>, Java can be used to write native stored procedures and user-defined functions.A PL/SQL procedure can also call external procedures or functions written in the Cprogramming language and stored in a shared library.In <strong>Oracle</strong>, there are four types of stored programs: functions, procedures, packages, andtriggers. These objects are very similar in construction, functionality,and usage to those