diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index a6db366643eb45cb425d938618faeb3915e70264..fe5b6990edf93768e567d04f90b4852d2b6aaa7f 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -2043,8 +2043,12 @@ int32_t validateSelectNodeList(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SArray* pS
   const char* msg1 = "too many items in selection clause";
   const char* msg2 = "functions or others can not be mixed up";
   const char* msg3 = "not support query expression";
-  const char* msg4 = "only support distinct one column or tag";
+  const char* msg4 = "invalid distinct query";
   const char* msg5 = "invalid function name";
+  const char* msg6 = "not support distinct mixed with agg function";
+  const char* msg7 = "not support distinct mixed with join"; 
+  const char* msg8 = "not support distinct mixed with groupby";
+  const char* msg9 = "not support distinct in nest query";
 
   // too many result columns not support order by in query
   if (taosArrayGetSize(pSelNodeList) > TSDB_MAX_COLUMNS) {
@@ -2056,6 +2060,7 @@ int32_t validateSelectNodeList(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SArray* pS
   }
 
   bool hasDistinct = false;
+  bool hasAgg      = false; 
   size_t numOfExpr = taosArrayGetSize(pSelNodeList);
   for (int32_t i = 0; i < numOfExpr; ++i) {
     int32_t outputIndex = (int32_t)tscNumOfExprs(pQueryInfo);
@@ -2067,6 +2072,7 @@ int32_t validateSelectNodeList(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SArray* pS
 
     int32_t type = pItem->pNode->type;
     if (type == SQL_NODE_SQLFUNCTION) {
+      hasAgg = true;
       pItem->pNode->functionId = isValidFunction(pItem->pNode->Expr.operand.z, pItem->pNode->Expr.operand.n);
       SUdfInfo* pUdfInfo = NULL;
       if (pItem->pNode->functionId < 0) {
@@ -2102,10 +2108,25 @@ int32_t validateSelectNodeList(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SArray* pS
     }
   }
 
+  
+  //TODO(dengyihao), refactor as function     
+  //handle distinct func mixed with other func 
   if (hasDistinct == true) {
     if (!isValidDistinctSql(pQueryInfo) ) {
       return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg4);
     }
+    if (hasAgg) {
+      return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg6);
+    }
+    if (joinQuery) {
+      return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg7);
+    }
+    if (pQueryInfo->groupbyExpr.numOfGroupCols  != 0) {
+      return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg8);
+    }
+    if (pQueryInfo->pDownstream != NULL) {
+      return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg9);
+    }
     pQueryInfo->distinct = true;
   }
   
@@ -8395,12 +8416,12 @@ static int32_t doValidateSubquery(SSqlNode* pSqlNode, int32_t index, SSqlObj* pS
   pSub->pUdfInfo = pUdfInfo;
   pSub->udfCopy = true;
 
+  pSub->pDownstream = pQueryInfo;
   int32_t code = validateSqlNode(pSql, p, pSub);
   if (code != TSDB_CODE_SUCCESS) {
     return code;
   }
 
-  pSub->pDownstream = pQueryInfo;
 
   // create dummy table meta info
   STableMetaInfo* pTableMetaInfo1 = calloc(1, sizeof(STableMetaInfo));
@@ -8509,6 +8530,7 @@ int32_t validateSqlNode(SSqlObj* pSql, SSqlNode* pSqlNode, SQueryInfo* pQueryInf
     if (validateGroupbyNode(pQueryInfo, pSqlNode->pGroupby, pCmd) != TSDB_CODE_SUCCESS) {
       return TSDB_CODE_TSC_INVALID_OPERATION;
     }
+    
 
     if (validateSelectNodeList(pCmd, pQueryInfo, pSqlNode->pSelNodeList, false, timeWindowQuery, true) !=
         TSDB_CODE_SUCCESS) {
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index 5a724af7bf17e4aa09eac880f6c6176db4bdd96d..008c5c0a4396a6ddcd70aecd9bbd8870e7e13850 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -1502,7 +1502,6 @@ void tscFreeSqlObj(SSqlObj* pSql) {
   tscFreeSqlResult(pSql);
   tscResetSqlCmd(pCmd, false);
 
-  memset(pCmd->payload, 0, (size_t)pCmd->allocSize);
   tfree(pCmd->payload);
   pCmd->allocSize = 0;