[TD-2236] add test cases.

tests/script/general/parser/groupby.sim

@@ -606,6 +606,44 @@ sql insert into t1 values ('2020-03-27 04:21:16.000', 1)('2020-03-27 04:31:17.00
 sql insert into t2 values ('2020-03-27 04:11:16.000', 1)('2020-03-27 04:11:17.000', 2) ('2020-03-27 04:11:18.000', 3) ('2020-03-27 04:11:19.000', 4) ; 
 sql insert into t2 values ('2020-03-27 04:21:16.000', 1)('2020-03-27 04:31:17.000', 2) ('2020-03-27 04:51:18.000', 3) ('2020-03-27 05:10:19.000', 4) ; 
 
+print =================>td-2236
+sql select first(ts),last(ts) from t1 group by c;
+if $rows != 4 then
+  return -1
+endi
+
+if $data00 != @20-03-27 04:11:16.000@ then
+  return -1
+endi
+
+if $data01 != @20-03-27 04:21:16.000@ then
+  return -1
+endi
+
+if $data10 != @20-03-27 04:11:17.000@ then
+  return -1
+endi
+
+if $data11 != @20-03-27 04:31:17.000@ then
+  return -1
+endi
+
+if $data20 != @20-03-27 04:11:18.000@ then
+  return -1
+endi
+
+if $data21 != @20-03-27 04:51:18.000@ then
+  return -1
+endi
+
+if $data30 != @20-03-27 04:11:19.000@ then
+  return -1
+endi
+
+if $data31 != @20-03-27 05:10:19.000@ then
+  return -1
+endi
+
 #sql select irate(c) from st where t1="1" and ts >= '2020-03-27 04:11:17.732' and ts < '2020-03-27 05:11:17.732'  interval(1m) sliding(15s) group by tbname,t1,t2;
 #if $rows != 40 then
 #  return -1