帮我优化一段sql：SELECT SUM(vin) AS vin_sum FROM (SELECT vin FROM hryt_gca_vehicle_audit_defect WHERE TO_CHAR(create_date,'yyyy mm iw') = TO_CHAR(Sysdate, 'yyyy mm iw') GROUP BY VIN ORDER BY dbms_random.value) WHERE rownum <= 10;

很高兴为您服务！这个SQL查询可以优化，您可以通过以下代码实现：

SELECT SUM(vin) AS vin_sum FROM
(
SELECT vin FROM
(
SELECT vin, rownum rn FROM
(
SELECT vin
FROM hryt_gca_vehicle_audit_defect
WHERE TO_CHAR(create_date,'yyyy mm iw') = TO_CHAR(Sysdate, 'yyyy mm iw')
GROUP BY VIN
ORDER BY dbms_random.value
)
)
WHERE rn <= 10
)

这个优化方案的思路是为内部查询添加行号，并且将ROWNUM筛选条件从外部查询中移除。这样效率更高，能够更快地获取结果。希望这个答案能帮助到您！

相关问题

帮我优化下这个sql ： SELECT t4.vin, t3.msg_id AS trip_id, t3.trip_start_time, t4.switch_value AS has_trip FROM ( SELECT * FROM dds.dwd_driving_calendar t1 WHERE t1.vin = 'LSJA24396MS179029' AND 1681745400001 > t1.trip_start_time AND 1681745400001 < t1.trip_end_time ) t3 LEFT JOIN ( SELECT * FROM dds.vehicle_journey_switch_history t2 WHERE t2.vin IN ( 'LSJA24396MS179029' ) ) t4 ON t3.vin = t4.vin AND t4.switch_key = 'vehicle_journey_data' AND '2023-04-17 23:30:00' > t4.create_time AND '2023-04-17 23:30:00' < t4.update_time

可以尝试优化以下几个方面：

1. 使用EXISTS替换LEFT JOIN

可以使用EXISTS来代替LEFT JOIN进行连接查询，因为EXISTS在查询到一条匹配的数据后就会停止，而LEFT JOIN需要查询完整个表再返回结果。

SELECT t3.vin, t3.msg_id AS trip_id, t3.trip_start_time, 
       t4.switch_value AS has_trip 
FROM dds.dwd_driving_calendar t3 
WHERE t3.vin = 'LSJA24396MS179029' 
  AND 1681745400001 > t3.trip_start_time 
  AND 1681745400001 < t3.trip_end_time
  AND EXISTS (
      SELECT 1 
      FROM dds.vehicle_journey_switch_history t4 
      WHERE t3.vin = t4.vin 
        AND t4.switch_key = 'vehicle_journey_data' 
        AND '2023-04-17 23:30:00' > t4.create_time 
        AND '2023-04-17 23:30:00' < t4.update_time
    )

2. 添加索引

在vin、trip_start_time、trip_end_time、switch_key、create_time和update_time列上添加索引，可以加速查询。

3. 不要使用SELECT *

在子查询中不要使用SELECT *，而是明确指定需要查询的列，可以减少不必要的数据读取和传输，提高查询效率。例如：

SELECT vin, msg_id AS trip_id, trip_start_time
FROM dds.dwd_driving_calendar 
WHERE vin = 'LSJA24396MS179029' 
  AND 1681745400001 > trip_start_time 
  AND 1681745400001 < trip_end_time

SELECT vin, switch_value
FROM dds.vehicle_journey_switch_history
WHERE vin IN ('LSJA24396MS179029') 
  AND switch_key = 'vehicle_journey_data' 
  AND '2023-04-17 23:30:00' > create_time 
  AND '2023-04-17 23:30:00' < update_time

MySQL优化：select brandName,have_vin_count,(select count(1) from epc_carmodel_skucount where ifnull(vin,'') <> '') as have_vin_sum_count, concat(round(have_vin_count/(select count(1) from epc_carmodel_skucount where ifnull(vin,'') <> '')*100, 2),'%') as have_vin_percent from (select b.brandName,count(distinct a.vehicleUUID) as have_vin_count from (select distinct vehicleUUID from epc_carmodel_skucount where ifnull(vin,'') <> '') a inner join ( select b.brandName,b.vehicleUUID from epc_material_sence_model a join ( select * from epc_bom_sence where brandName not in ('演示','测试','客服内测') and ifnull(brandName,'') <> '' and brandName not like '火星%' and brandName not like '原厂%' ) b on a.oeId=b.oeId where a.categoryName='火花塞' ) b on a.vehicleUUID=b.vehicleUUID group by b.brandName

这段 SQL 语句是查询汽车品牌的火花塞车型中，有 VIN 码的车型数量及占比。其中使用了子查询和连接查询，可能会有性能问题。建议优化如下：

1. 尽量避免在子查询中使用聚合函数，可以将子查询的结果存储到临时表中，以提高查询效率。

2. 将子查询中的 ifnull(vin,'') <> '' 转换为 vin IS NOT NULL AND vin <> ''，可以利用索引优化查询。

3. 使用 JOIN 操作时，尽量通过 ON 子句指定连接条件，避免使用 WHERE 子句进行过滤，提高查询效率。

优化后的 SQL 语句如下：

SELECT 
    b.brandName,
    COUNT(DISTINCT a.vehicleUUID) AS have_vin_count,
    COUNT(DISTINCT c.vehicleUUID) AS have_vin_sum_count,
    CONCAT(ROUND(COUNT(DISTINCT a.vehicleUUID) / COUNT(DISTINCT c.vehicleUUID) * 100, 2), '%') AS have_vin_percent
FROM 
    epc_carmodel_skucount a
    INNER JOIN (
        SELECT 
            b.brandName,
            b.vehicleUUID 
        FROM 
            epc_material_sence_model a 
            JOIN (
                SELECT * 
                FROM epc_bom_sence 
                WHERE brandName NOT IN ('演示', '测试', '客服内测') 
                    AND IFNULL(brandName, '') <> '' 
                    AND brandName NOT LIKE '火星%' 
                    AND brandName NOT LIKE '原厂%'
            ) b 
            ON a.oeId = b.oeId 
        WHERE a.categoryName = '火花塞'
    ) b 
    ON a.vehicleUUID = b.vehicleUUID 
    AND a.vin IS NOT NULL 
    AND a.vin <> ''
    LEFT JOIN epc_carmodel_skucount c 
    ON c.vin IS NOT NULL 
    AND c.vin <> ''
GROUP BY 
    b.brandName

这样，可以避免子查询中的聚合函数，使用 INNER JOIN 操作指定连接条件，同时使用 LEFT JOIN 操作获取所有有 VIN 码的车型数量，从而提高查询效率。