SQL/DDL Implementation › Implementing Restrictor and Positioner Functionality › Example of WHERE Clause Containing NOT Logic

Example of WHERE Clause Containing NOT Logic

EXEC SQL                                              
     DECLARE MYVIEWCURSOR CURSOR  FOR                 
          SELECT 8 FROM MYVIEW                        
               WHERE       KEY1   =   :HOSTVAR1       
               AND NOT    (KEY1   =   :HOSTVAR1  AND  
                           KEY2   <   :HOSTVAR2     )
               AND NOT    (KEY1   =   :HOSTVAR1  AND  
                           KEY2   =   :HOSTVAR2  AND  
                           KEY3   <   :HOSTVAR3     ))
          ORDER BY         KEY1   ASC,                
                           KEY2   ASC,                
                           KEY3   ASC                 
END-EXEC                                             

The relative efficiency of these two methods depends on the target RDBMS; for example, Oracle tables with large amounts of data perform better using NOT logic.