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

<strong>Solution</strong> <strong>Guide</strong> <strong>for</strong> <strong>Migrating</strong> <strong>Oracle</strong> on UNIX to SQL Server on Windows 119Operation <strong>Oracle</strong> SQL ServerON UPDATECASCADE }NO ACTION}CREATE TABLEtable_name(…,column_name datatype,…,[ CONSTRAINTconstraint_name ]FOREIGN KEY(column_name [,…]REFERENCESref_table_name(ref_column_name[, …])ON UPDATE { CASCADE |NO ACTION}TriggersTriggers are used to en<strong>for</strong>ce more complex business rules than can be en<strong>for</strong>ced usingconstraints. Triggers are stored procedures that are implicitly executed when certain datamodification (using data manipulation language statements, also known as DML) isper<strong>for</strong>med against tables and views. In <strong>Oracle</strong>, there can be up to twelve combinations oftrigger executions (actions) based on:● DML operation: INSERT, UPDATE, DELETE● Timing: BEFORE, AFTER● Level: ROW, STATEMENTTable 6.18 evaluates SQL Server support <strong>for</strong> the <strong>Oracle</strong> trigger functionality.Table 6.18: Functionality of <strong>Oracle</strong> Triggers Mapped to SQL ServerTrigger Feature <strong>Oracle</strong> SQL ServerDML – INSERT Yes YesDML – UPDATE Column/Row RowDML – DELETE Yes YesTiming – BEFORE Yes Yes (INSTEAD OF)Timing – AFTER Yes YesLevel Row/Statemen tRowViews – INSTEAD OF Yes YesMultiple triggers per action Yes Yes (first/last specified)The SQL Server INSTEAD OF triggers are equivalent to <strong>Oracle</strong>’s BEFORE triggers.When migrating triggers from <strong>Oracle</strong>, the only drawback is that SQL Server does notsupport statement-level triggers. However, there are two pseudo-tables, inserted anddeleted, that are populated during the trig ger execution and which can be used tosimulate statement-level operations. These insertedand deleted pseudo tables aresimilar to the :old and :new pseudo-rows in <strong>Oracle</strong> and are populated with all (multiple)rows affected by the trigger execution. The SQL Server deleted and inserted pseudotablesare available by default and are not specified as part of the trigger definition. In