[td-1752] add test cases.

tests/script/general/parser/constCol.sim

@@ -357,4 +357,32 @@ print ========================> td-1756
 sql_error select * from t1 where ts>now-1y
 sql_error select * from t1 where ts>now-1n
 
+print ========================> td-1752
+sql select * from st2 where t2 < 200 and t2 is not null;
+if $rows != 1 then
+  return -1
+endi
+
+if $data00 != @19-12-09 16:27:35.000@ then
+  return -1
+endi
+
+if $data01 != 2 then
+  return -1
+endi
+
+if $data02 != 1 then
+  return -1
+endi
+
+sql select * from st2 where t2 > 200 or t2 is null;
+if $rows != 0 then
+  return -1
+endi
+
+sql select * from st2 where t2 < 200 and t2 is null;
+if $rows != 0 then
+  return -1
+endi
+
 system sh/exec.sh -n dnode1 -s stop -x SIGINT