IOTDB入门（六）

当连接到IOTDB数据库并创建了存储组和时间序列后，您可以执行各种操作来读取、写入和查询数据。以下是一些常见操作的示例代码：

1. 聚合查询：

   String sql = "SELECT AVG(temperature), MAX(humidity) FROM root.sg1.device1 WHERE time >= 1629792000000 AND time <= 1629878400000 GROUP BY ([1h, 10m])";
   SessionDataSet dataSet = session.executeQueryStatement(sql);
   while (dataSet.hasNext()) {
       RowRecord rowRecord = dataSet.next();
       System.out.println("Time: " + rowRecord.getTimestamp());
       System.out.println("Average Temperature: " + rowRecord.getFields().get(0).getFloatV());
       System.out.println("Max Humidity: " + rowRecord.getFields().get(1).getFloatV());
   }
   

2. 查询数据并进行分页：

   String sql = "SELECT temperature, humidity FROM root.sg1.device1 WHERE time >= 1629792000000 AND time <= 1629878400000";
   int limit = 10; // 每页数据条数
   int offset = 0; // 偏移量
   while (true) {
       String pageSql = sql + " LIMIT " + limit + " OFFSET " + offset;
       SessionDataSet dataSet = session.executeQueryStatement(pageSql);
       if (!dataSet.hasNext()) {
           break;
       }
       while (dataSet.hasNext()) {
           RowRecord rowRecord = dataSet.next();
           System.out.println("Time: " + rowRecord.getTimestamp());
           System.out.println("Temperature: " + rowRecord.getFields().get(0).getFloatV());
           System.out.println("Humidity: " + rowRecord.getFields().get(1).getFloatV());
       }
       offset += limit;
   }
   

3. 使用时间过滤条件查询数据：

   long startTime = 1629792000000L; // 开始时间
   long endTime = 1629878400000L; // 结束时间
   String sql = "SELECT temperature, humidity FROM root.sg1.device1 WHERE time > " + startTime + " AND time < " + endTime;
   SessionDataSet dataSet = session.executeQueryStatement(sql);
   while (dataSet.hasNext()) {
       RowRecord rowRecord = dataSet.next();
       System.out.println("Time: " + rowRecord.getTimestamp());
       System.out.println("Temperature: " + rowRecord.getFields().get(0).getFloatV());
       System.out.println("Humidity: " + rowRecord.getFields().get(1).getFloatV());
   }
   

4. 执行聚合函数查询并使用别名：

   String sql = "SELECT AVG(temperature) AS avg_temp, MAX(humidity) AS max_humidity FROM root.sg1.device1 WHERE time >= 1629792000000 AND time <= 1629878400000";
   SessionDataSet dataSet = session.executeQueryStatement(sql);
   if (dataSet.hasNext()) {
       RowRecord rowRecord = dataSet.next();
       System.out.println("Average Temperature: " + rowRecord.getFields().get("avg_temp").getFloatV());
       System.out.println("Max Humidity: " + rowRecord.getFields().get("max_humidity").getFloatV());
   }
   

这些示例代码展示了更多的操作，包括聚合查询、分页查询、时间过滤条件查询和使用别名。您可以根据具体的需求和业务场景进行进一步的操作和扩展。