SELECT bd.SENSOR_ID as sensorId, si.sensor_name AS sensorName, si.dam_id as damId, bd.WATER_LEVEL AS waterLevel, bd.WATER_TOP AS waterTop , bd.HOLE_DEPTH AS holeDepth, td.height-bd.WATER_TOP AS buryDepth FROM ( SELECT DAM_ID,SENSOR_ID, WATER_LEVEL,WATER_TOP, HOLE_DEPTH, ROW_NUMBER ( ) OVER ( PARTITION BY SENSOR_ID ORDER BY UPLOAD_TIME DESC ) AS RN FROM B_DAM_WATER_LEVEL ) bd LEFT JOIN sensor_info si ON bd.SENSOR_ID = si.sensor_id LEFT JOIN tailings_dam td ON bd.DAM_ID=td.dam_id WHERE bd.RN = 1 这个语句查询大量数据太慢了，优化一下

有几种可能的优化方式：

1. 添加索引：可以在 B_DAM_WATER_LEVEL 表的 SENSOR_ID、UPLOAD_TIME 字段上添加索引，以加快查询速度。

2. 分离子查询：将子查询的结果存储在一个临时表中，然后再与其他表进行 JOIN 操作。这样可以避免每次都进行子查询，提高查询速度。

3. 减少 JOIN 操作：可以先将 SENSOR_ID、DAM_ID 两个表的结果进行 JOIN 操作，再将结果与 B_DAM_WATER_LEVEL 表进行 JOIN 操作。这样可以减少 JOIN 操作的数量，提高查询速度。

综上所述，可以尝试以下优化方式：

-- 添加索引
CREATE INDEX idx_sensor_id ON B_DAM_WATER_LEVEL (SENSOR_ID);
CREATE INDEX idx_upload_time ON B_DAM_WATER_LEVEL (UPLOAD_TIME);

-- 分离子查询
WITH latest_data AS (
    SELECT SENSOR_ID, DAM_ID, MAX(UPLOAD_TIME) AS latest_time
    FROM B_DAM_WATER_LEVEL
    GROUP BY SENSOR_ID, DAM_ID
)
SELECT
    bd.SENSOR_ID AS sensorId,
    si.sensor_name AS sensorName,
    si.dam_id AS damId,
    bd.WATER_LEVEL AS waterLevel,
    bd.WATER_TOP AS waterTop,
    bd.HOLE_DEPTH AS holeDepth,
    td.height - bd.WATER_TOP AS buryDepth
FROM latest_data ld
JOIN B_DAM_WATER_LEVEL bd
    ON ld.SENSOR_ID = bd.SENSOR_ID
    AND ld.DAM_ID = bd.DAM_ID
    AND ld.latest_time = bd.UPLOAD_TIME
LEFT JOIN sensor_info si
    ON bd.SENSOR_ID = si.sensor_id
LEFT JOIN tailings_dam td
    ON bd.DAM_ID = td.dam_id;

希望这可以帮助你优化查询语句。