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sql优化下查询速度

对于这个 SQL 查询语句，可以考虑以下优化方案：

1.使用索引：对于查询中涉及到的表，可以对关联的字段建立相应的索引，例如在 B_DAM_WATER_LEVEL 表中可以为 SENSOR_ID 和 UPLOAD_TIME 字段建立索引，在 sensor_info 表中为 sensor_id 字段建立索引，在 tailings_dam 表中为 dam_id 字段建立索引。这样可以加快查询效率。

2.使用子查询替代连接查询：可以将子查询中的结果作为一个虚拟表，然后与 sensor_info 表和 tailings_dam 表进行连接，例如：

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 
     JOIN 
    (SELECT sensor_id, 
            sensor_name,
            dam_id 
     FROM sensor_info) si 
     ON bd.SENSOR_ID = si.sensor_id 
     JOIN 
    (SELECT dam_id, 
            height 
     FROM tailings_dam) td 
     ON bd.dam_id = td.dam_id 
WHERE bd.RN = 1;

3.使用 WITH 语句：使用 WITH 语句将子查询的结果作为一个临时表，然后对临时表进行操作，例如：

WITH latest_water_level AS (
    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
    WHERE RN = 1
)
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_water_level bd 
    JOIN 
    (SELECT sensor_id, 
            sensor_name,
            dam_id 
     FROM sensor_info) si 
     ON bd.SENSOR_ID = si.sensor_id 
     JOIN 
    (SELECT dam_id, 
            height 
     FROM tailings_dam) td 
     ON bd.dam_id = td.dam_id;

以上是一些常见的 SQL 查询优化方案，可以根据实际情况进行选择和调整。