[td-225]fix bug in sim.

tests/script/general/parser/function.sim

@@ -1074,7 +1074,7 @@ sql insert into t0 values('2020-1-1 1:4:10', 10);
 
 sql insert into t1 values('2020-1-1 1:1:2', 2);
 print ===========================>td-4739
-sql select diff(val) from (select derivative(k, 1s, 0) from t1);
+sql select diff(val) from (select derivative(k, 1s, 0) val from t1);
 if $rows != 0 then
   return -1
 endi