private String parseAliasNode(IoTDBSqlParser.AliasContext ctx) {
    String alias;
    if (ctx.constant() != null) {
      alias = parseConstant(ctx.constant());
      if (PathUtils.isRealNumber(alias)
          || !TsFileConstant.IDENTIFIER_PATTERN.matcher(alias).matches()) {
        throw new SemanticException("Not support for this alias, Please enclose in back quotes.");
      }
    } else {
      alias = parseNodeString(ctx.identifier().getText());
    }
    return alias;
  }
Function for parsing AliasNode.

@throws SemanticException if the alias pattern is not supported
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/parser/ASTVisitor.java