why I get _IORC_ error?

[ping]

data master;   

input dt $ dept $ sales;   

datalines;       

DEC-2013 PC 2000       

NOV-2013 PC 1500       

DEC-2012 MOBILE 3000   

;

run;

DATA lkup;

input dept $ percent; datalines;    

  PC 0.4   

  MOBILE 0.6 ;

run;

proc sql;   

create index dept on lkup(dept);   

quit;

data merged;   

set master;   

set lkup key=dept;   

x=_IORC_;

run;

I am getting error on second row, it should find match and no error is reported. Can anyone explain me what's wrong in the code?

[ping]

dt=NOV-2013 dept=PC sales=1500 percent=0.4 x=1230015 _ERROR_=1 _IORC_=1230015 _N_=2

[Tom · Accepted solution]

Try adding /UNIQUE option.

set lkup key=dept / unique;

[ping]

Works. Thanks a bunch.