IOTDB入门（六）

【摘要】 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：聚合查询：String sql = "SELECT AVG(temperature), MAX(humidity) FROM root.sg1.device1 WHERE time >= 1629792000000 AND time <= 1629878400000 G...
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：

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());
}
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;
}
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());
}
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。