如下代码:
data stock(index=(partno));
input PARTNO $ DESC $ INSTOCK @17 RECDATE date7. @25 PRICE;
format recdate date7.;
cards;
K89R seal 34 27jul95 245.00
M4J7 sander 98 20jun95 45.88
LK43 filter 121 19may96 10.99
MN21 brace 43 10aug96 27.87
BC85 clamp 80 16aug96 9.55
NCF3 valve 198 20mar96 24.50
KJ66 cutter 6 18jun96 19.77
UYN7 rod 211 09sep96 11.55
JD03 switch 383 09jan97 13.99
BV1E timer 26 03jan97 34.50
;
run;
data addinv;
input PARTNO $ NWSTOCK;
cards;
K89R 55
LK43 43
MN21 73
UYN7 108
JD03 55
;
data stock;
modify stock addinv;
by partno;
RECDATE=today();
INSTOCK=instock+nwstock;
*if _iorc_=0 then replace;
run;
我程序运行把if语句注释掉,运行结果仍然可以更新,我想知道这条语句的作用是什么?