fix: some prblems of parser and planner

include/util/taoserror.h

@@ -637,6 +637,7 @@ int32_t* taosGetErrno();
 #define TSDB_CODE_PAR_COMMENT_TOO_LONG          TAOS_DEF_ERROR_CODE(0, 0x264E)
 #define TSDB_CODE_PAR_NOT_ALLOWED_FUNC          TAOS_DEF_ERROR_CODE(0, 0x264F)
 #define TSDB_CODE_PAR_NOT_ALLOWED_WIN_QUERY     TAOS_DEF_ERROR_CODE(0, 0x2650)
+#define TSDB_CODE_PAR_INVALID_DROP_COL          TAOS_DEF_ERROR_CODE(0, 0x2651)
 
 //planner
 #define TSDB_CODE_PLAN_INTERNAL_ERROR           TAOS_DEF_ERROR_CODE(0, 0x2700)

source/libs/parser/src/parTranslater.c

@@ -4454,8 +4454,10 @@ static int32_t buildUpdateTagValReq(STranslateContext* pCxt, SAlterTableStmt* pS
 
   pReq->isNull = (TSDB_DATA_TYPE_NULL == pStmt->pVal->node.resType.type);
   pReq->nTagVal = pStmt->pVal->node.resType.bytes;
-  char* pVal = nodesGetValueFromNode(pStmt->pVal);
-  pReq->pTagVal = IS_VAR_DATA_TYPE(pStmt->pVal->node.resType.type) ? pVal + VARSTR_HEADER_SIZE : pVal;
+  if (TSDB_DATA_TYPE_NCHAR == pStmt->pVal->node.resType.type) {
+    pReq->nTagVal = pReq->nTagVal * TSDB_NCHAR_SIZE;
+  }
+  pReq->pTagVal = nodesGetValueFromNode(pStmt->pVal);
 
   return TSDB_CODE_SUCCESS;
 }
@@ -4479,6 +4481,9 @@ static int32_t buildAddColReq(STranslateContext* pCxt, SAlterTableStmt* pStmt, S
 
 static int32_t buildDropColReq(STranslateContext* pCxt, SAlterTableStmt* pStmt, STableMeta* pTableMeta,
                                SVAlterTbReq* pReq) {
+  if (2 == getNumOfColumns(pTableMeta)) {
+    return generateSyntaxErrMsg(&pCxt->msgBuf, TSDB_CODE_PAR_INVALID_DROP_COL);
+  }
   SSchema* pSchema = getColSchema(pTableMeta, pStmt->colName);
   if (NULL == pSchema) {
     return generateSyntaxErrMsg(&pCxt->msgBuf, TSDB_CODE_PAR_INVALID_COLUMN, pStmt->colName);

source/libs/parser/src/parUtil.c

@@ -169,6 +169,8 @@ static char* getSyntaxErrFormat(int32_t errCode) {
              "And, cannot be mixed with other non scalar functions or columns.";
     case TSDB_CODE_PAR_NOT_ALLOWED_WIN_QUERY:
       return "Window query not supported, since the result of subquery not include valid timestamp column";
+    case TSDB_CODE_PAR_INVALID_DROP_COL:
+      return "No columns can be dropped";
     case TSDB_CODE_OUT_OF_MEMORY:
       return "Out of memory";
     default: