diff --git a/src/client/src/tscPrepare.c b/src/client/src/tscPrepare.c
index 0df1c7ddc514f133f8c4b53852613b8c212ecfb6..b996dd958ae432300391a104f94a4cfe27f0858d 100644
--- a/src/client/src/tscPrepare.c
+++ b/src/client/src/tscPrepare.c
@@ -613,11 +613,13 @@ int taos_stmt_execute(TAOS_STMT* stmt) {
     if (sql == NULL) {
       ret = TSDB_CODE_TSC_OUT_OF_MEMORY;
     } else {
-      taosTFree(pStmt->pSql->sqlstr);
-      pStmt->pSql->sqlstr = sql;
-      SSqlObj* pSql = taos_query((TAOS*)pStmt->taos, pStmt->pSql->sqlstr);
-      ret = taos_errno(pSql);
-      taos_free_result(pSql);
+      if (pStmt->pSql != NULL) {
+        taos_free_result(pStmt->pSql);
+        pStmt->pSql = NULL;
+      }
+      pStmt->pSql = taos_query((TAOS*)pStmt->taos, sql);
+      ret = taos_errno(pStmt->pSql);
+      free(sql);
     }
   }
   return ret;
diff --git a/src/client/src/tscSub.c b/src/client/src/tscSub.c
index 0e1be926f44c2ee302c26a6695f4b93679194430..76bce19668433d8819d44c8f272ad62b1d6dd034 100644
--- a/src/client/src/tscSub.c
+++ b/src/client/src/tscSub.c
@@ -405,16 +405,20 @@ TAOS_SUB *taos_subscribe(TAOS *taos, int restart, const char* topic, const char
   return pSub;
 }
 
-void taos_free_result_imp(SSqlObj* pSql, int keepCmd);
-
 TAOS_RES *taos_consume(TAOS_SUB *tsub) {
   SSub *pSub = (SSub *)tsub;
   if (pSub == NULL) return NULL;
 
   tscSaveSubscriptionProgress(pSub);
 
-  SSqlObj* pSql = pSub->pSql;
+  SSqlObj *pSql = pSub->pSql;
   SSqlRes *pRes = &pSql->res;
+  SSqlCmd *pCmd = &pSql->cmd;
+  STableMetaInfo *pTableMetaInfo = tscGetTableMetaInfoFromCmd(pCmd, pCmd->clauseIndex, 0);
+  SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(pCmd, 0);
+  if (taosArrayGetSize(pSub->progress) > 0) { // fix crash in single tabel subscription
+    pQueryInfo->window.skey = ((SSubscriptionProgress*)taosArrayGet(pSub->progress, 0))->key;
+  }
 
   if (pSub->pTimer == NULL) {
     int64_t duration = taosGetTimestampMs() - pSub->lastConsumeTime;
@@ -436,8 +440,6 @@ TAOS_RES *taos_consume(TAOS_SUB *tsub) {
       tscDebug("table synchronization completed");
     }
 
-    SQueryInfo* pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
-    
     uint32_t type = pQueryInfo->type;
     tscFreeSqlResult(pSql);
     pRes->numOfRows = 1;
@@ -445,7 +447,7 @@ TAOS_RES *taos_consume(TAOS_SUB *tsub) {
     pSql->cmd.command = TSDB_SQL_SELECT;
     pQueryInfo->type = type;
 
-    tscGetTableMetaInfoFromCmd(&pSql->cmd, 0, 0)->vgroupIndex = 0;
+    pTableMetaInfo->vgroupIndex = 0;
 
     pSql->fp = asyncCallback;
     pSql->fetchFp = asyncCallback;
diff --git a/tests/examples/c/makefile b/tests/examples/c/makefile
index f9653c9c9678f572190f2f54ac10c039e8b86a44..7293a22c11d7c6049c220ca0951b5969fa344114 100644
--- a/tests/examples/c/makefile
+++ b/tests/examples/c/makefile
@@ -4,22 +4,24 @@
 ROOT=./
 TARGET=exe
 LFLAGS = '-Wl,-rpath,/usr/local/taos/driver/' -ltaos -lpthread -lm -lrt
-CFLAGS = -O3 -g -Wall -Wno-deprecated -fPIC -Wno-unused-result -Wconversion -Wno-char-subscripts -D_REENTRANT -Wno-format -D_REENTRANT -DLINUX -msse4.2 -Wno-unused-function -D_M_X64 \
-	-I/usr/local/taos/include -std=gnu99
+CFLAGS = -O3 -g -Wall -Wno-deprecated -fPIC -Wno-unused-result -Wconversion \
+	-Wno-char-subscripts -D_REENTRANT -Wno-format -D_REENTRANT -DLINUX \
+	-msse4.2 -Wno-unused-function -D_M_X64 -I/usr/local/taos/include -std=gnu99
 
 all: $(TARGET)
 
 exe:
-	gcc $(CFLAGS) ./asyncdemo.c -o $(ROOT)/asyncdemo $(LFLAGS)
-	gcc $(CFLAGS) ./demo.c -o $(ROOT)/demo $(LFLAGS)
-	gcc $(CFLAGS) ./prepare.c -o $(ROOT)/prepare $(LFLAGS)
-	gcc $(CFLAGS) ./stream.c -o $(ROOT)/stream $(LFLAGS)
+	gcc $(CFLAGS) ./asyncdemo.c -o $(ROOT)asyncdemo $(LFLAGS)
+	gcc $(CFLAGS) ./demo.c -o $(ROOT)demo $(LFLAGS)
+	gcc $(CFLAGS) ./prepare.c -o $(ROOT)prepare $(LFLAGS)
+	gcc $(CFLAGS) ./stream.c -o $(ROOT)stream $(LFLAGS)
 	gcc $(CFLAGS) ./subscribe.c -o $(ROOT)subscribe $(LFLAGS)
 	gcc $(CFLAGS) ./apitest.c -o $(ROOT)apitest $(LFLAGS)
 
 clean:
-	rm $(ROOT)/asyncdemo
-	rm $(ROOT)/demo
-	rm $(ROOT)/prepare
-	rm $(ROOT)/stream
-	rm $(ROOT)/subscribe
+	rm $(ROOT)asyncdemo
+	rm $(ROOT)demo
+	rm $(ROOT)prepare
+	rm $(ROOT)stream
+	rm $(ROOT)subscribe
+	rm $(ROOT)apitest
diff --git a/tests/examples/c/prepare.c b/tests/examples/c/prepare.c
index ca0942035ad9f6016993aeb4f7521a9c31dc8175..7a70b744ee8561459318aa456160a54b8c6270a8 100644
--- a/tests/examples/c/prepare.c
+++ b/tests/examples/c/prepare.c
@@ -195,11 +195,15 @@ int main(int argc, char *argv[])
     taos_print_row(temp, row, fields, num_fields);
     printf("%s\n", temp);
   }
+  if (rows == 2) {
+    printf("two rows are fetched as expectation\n");
+  } else {
+    printf("expect two rows, but %d rows are fetched\n", rows);
+  }
 
   taos_free_result(result);
   taos_stmt_close(stmt);
-  
-  printf("Data has been written, Please press enter to return");
-  return getchar();
+
+  return 0;
 }
 
diff --git a/tests/examples/c/subscribe.c b/tests/examples/c/subscribe.c
index db5ad34ee7064978a888fc0e1cedc62aabc5a6a3..8368af18f7831d9c2cbb7402104b1c59042eda72 100644
--- a/tests/examples/c/subscribe.c
+++ b/tests/examples/c/subscribe.c
@@ -56,7 +56,7 @@ void check_row_count(int line, TAOS_RES* res, int expected) {
 
 
 void do_query(TAOS* taos, const char* sql) {
-  TAOS_RES* res = taos_query(taos, "drop database if exists test;");
+  TAOS_RES* res = taos_query(taos, sql);
   taos_free_result(res);
 }