COALESCE(SUM(d.金额), 0,0)
时间: 2024-04-21 22:18:00 浏览: 20
COALESCE(SUM(d.金额), 0,0) 是一个SQL语句中的函数,它的作用是返回参数列表中第一个非空的值。在这个例子中,它的参数列表是(SUM(d.金额), 0, 0),即先计算SUM(d.金额)的值,如果该值为空,则返回0。如果SUM(d.金额)的值不为空,那么COALESCE函数会返回SUM(d.金额)的值。所以,COALESCE(SUM(d.金额), 0,0)的结果要么是SUM(d.金额)的值,要么是0。
相关问题
SELECT unit.*, COALESCE(sum(detail.order_money), 0) as order_amount, COALESCE(sum(detail.one_commission), 0) as one_commission, COALESCE(sum(detail.two_commission), 0) as two_commission, COALESCE((sum(detail.two_commission) + sum(detail.one_commission)), 0) as total_commission FROM profit_dividend_unit unit LEFT OUTER JOIN profit_dividend_detail detail ON unit.dividend_code = detail.dividend_code GROUP BY unit.unit_id 这个不使用GROUP BY,怎么写?
如果不使用 GROUP BY 子句,则可以使用子查询来实现相同的结果。例如:
SELECT unit.*,
(SELECT COALESCE(SUM(order_money), 0) FROM profit_dividend_detail WHERE dividend_code = unit.dividend_code) as order_amount,
(SELECT COALESCE(SUM(one_commission), 0) FROM profit_dividend_detail WHERE dividend_code = unit.dividend_code) as one_commission,
(SELECT COALESCE(SUM(two_commission), 0) FROM profit_dividend_detail WHERE dividend_code = unit.dividend_code) as two_commission,
(SELECT COALESCE(SUM(one_commission), 0) + COALESCE(SUM(two_commission), 0) FROM profit_dividend_detail WHERE dividend_code = unit.dividend_code) as total_commission
FROM profit_dividend_unit unit;
该语句将返回与原始查询相同的结果,但是使用了子查询来替代 GROUP BY 子句。
优化以下SQL,给出优化后的SQL:SELECT un.*, sta.*, CASE WHEN COALESCE(un.lot_time, 0) > COALESCE(sta.dock_time_limit, 0) THEN COALESCE(un.lot_time, 0) - COALESCE(sta.dock_time_limit, 0) ELSE 0 END AS lotDuration FROM unload_over_time un LEFT JOIN ( SELECT parking_lot_code, dock_time_limit FROM stall_infor WHERE data_state = 0 AND delete_state = 1 AND industry_park_code='YQWQML' ) sta ON un.parking_lot_code = sta.parking_lot_code INNER JOIN ( SELECT DISTINCT plate_number FROM supplier_info WHERE data_state = 0 AND delete_state = 1 AND arrived_atetime IS NOT NULL AND left_datetime IS NULL AND industry_park_code='YQWQML' ) sup ON un.plate_number = sup.plate_number WHERE un.data_state = 0 AND un.delete_state = 1 AND un.is_out_of_time = 1 AND un.industry_park_code='YQWQML' AND un.parking_lot_code IN ( SELECT DISTINCT parking_lot_code FROM unload_over_time WHERE data_state = 0 AND delete_state = 1 AND is_out_of_time = 1 AND industry_park_code='YQWQML' )
优化后的SQL如下:
```sql
SELECT un.*, sta.*,
CASE WHEN COALESCE(un.lot_time, 0) > COALESCE(sta.dock_time_limit, 0) THEN COALESCE(un.lot_time, 0) - COALESCE(sta.dock_time_limit, 0) ELSE 0 END AS lotDuration
FROM unload_over_time un
LEFT JOIN stall_infor sta ON un.parking_lot_code = sta.parking_lot_code
INNER JOIN supplier_info sup ON un.plate_number = sup.plate_number
WHERE un.data_state = 0
AND un.delete_state = 1
AND un.is_out_of_time = 1
AND un.industry_park_code='YQWQML'
AND EXISTS (
SELECT 1
FROM unload_over_time uot
WHERE uot.data_state = 0
AND uot.delete_state = 1
AND uot.is_out_of_time = 1
AND uot.industry_park_code='YQWQML'
AND uot.parking_lot_code = un.parking_lot_code
)
AND EXISTS (
SELECT 1
FROM stall_infor si
WHERE si.data_state = 0
AND si.delete_state = 1
AND si.industry_park_code='YQWQML'
AND si.parking_lot_code = un.parking_lot_code
)
AND EXISTS (
SELECT 1
FROM supplier_info sp
WHERE sp.data_state = 0
AND sp.delete_state = 1
AND sp.arrived_atetime IS NOT NULL
AND sp.left_datetime IS NULL
AND sp.industry_park_code='YQWQML'
AND sp.plate_number = un.plate_number
)
```
优化后的SQL做了以下几点改进:
1. 将子查询转化为 EXISTS 子句,避免使用 DISTINCT 关键字和 IN 子查询,提高查询性能。
2. 将 LEFT JOIN 子查询转化为直接的 LEFT JOIN 操作,避免嵌套查询,简化SQL结构。
3. 合并了相同的过滤条件,减少重复的条件判断。
优化后的SQL应该能够提高查询性能。但请注意,在实际应用中,最佳的优化方案还需要根据具体的数据量、索引等因素进行调整和测试。
相关推荐
![zip](https://img-home.csdnimg.cn/images/20210720083736.png)
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)