索引（DB2）

CREATE INDEX IDX_1 ON EMP  
   (ID ASC) ALLOW REVERSE SCANS; 
 CREATE INDEX IDX_1 ON EMP  
   (ID ASC) DISALLOW REVERSE SCANS;

CREATE INDEX IDX_1 ON EMP  
   (ID ASC) /*ALLOW REVERSE SCANS*/; 
 CREATE INDEX IDX_1 ON EMP  
   (ID ASC) /*DISALLOW REVERSE SCANS*/;

CREATE INDEX IDXSC.IDX_1 ON EMP (ID ASC);

CREATE INDEX IDX_1 ON EMP (ID ASC);