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 189NULLIFReturns a nullvalue if the twospecifiedexpressionsare equivalentNULLIF(SYSDATE,SYSDATE)returns NULLNULLIFNULLIF(GETDATE (),GETDATE ())returns NULLDECODE Used to DECODE(DIS CASECASEevaluate the CONTINUED, DISCONTINUEvalues with "if- 0, 'No', 1, 'Yes',Delse" logic. 'NA')WHEN 0 THEN'No'WHEN 1 THEN'Yes'ELSE 'NA'ENDCASEUsed toevaluate thevalues with "if-CASEdiscontinuedWHEN 0 THENCASECASEdiscontinuedWHEN 0 THENelse" logic. 'No''No'WHEN 1 THEN'Yes'ELSE 'NA'ENDWHEN 1 THEN'Yes'ELSE 'NA'ENDQueriesThe SELECT statement is used to query the database and retrieve data. SELECT can becombined with some DDL and DML statements to per<strong>for</strong>m relational operations. Thefollowing different clauses commonly used with SELECT in <strong>Oracle</strong> and SQL Server arediscussed in the remainder of this section.● Simple queries● Joins● Database links● Group by● Case● Set operators● RownumOptimizer hints are not covered in this guidance. Both <strong>Oracle</strong> and SQL Server use costthatcan be used to influence the optimizer. Thebased optimizers and offer hintsoptimizer hints used with <strong>Oracle</strong> are not available in SQL Server. For the various types ofhints available in SQL Server refer tohttp://msdn.microsoft.com/library/default.asp?url=/library/enus/acdata/ac_8_qd_03_8upf.asp.Simple QueriesA simple query is defined as a SELECT statement that retrieves data from a single tablewith or without filter condition. Becausethis is a standard command, there are nodifferences in syntax or usage between <strong>Oracle</strong> and SQL Server. The following example isa valid statement <strong>for</strong> both <strong>Oracle</strong> and SQL Server.