如何从父表的两个子表中获取值

Question

我有三个表（发票，费率，费率_slap）我在发票表中有重量和 no_of_package 如果发票.重量 < = rate.weight 那么它将返回该表 rate.weight else weight < = rate_slap.weight 然后它将返回该表rate_slap.weight

但返回任何一个表值，而不是从两者中返回。

SELECT 
rate.`minimum_wgt`, 
slap.`slap_weight`
FROM m_ac_customer_rate rate
LEFT JOIN m_ac_customer_rate_slap slap ON (rate.minimum_wgt<=15) 
OR (slap.slap_weight<=15)
WHERE rate.customer_rate_id=slap.customer_rate_master 
AND `customer_name`=1007
AND `destination_name`=3
AND `service_type`=1
AND `shipment_type`='D'
AND `payment_mode`='CASH';

样本数据

发票表

invoice_no,weight,total_carton
 2142423,   10.4,     5

费率表

invoice_no,weight,rate_per_kg
2142423 , 15.8,      150.00

rate_slap 表

rateslap_id,weight,rate_per_kg
2142423 , 10.8,      10.00

Answer 1

这将在子查询中选择两个重量（如果存在）以及发票重量，然后在主查询中执行 CASE... 以选择正确的一个

SELECT no_of_package, 
  CASE WHEN weight <= rate_weight THEN rate_weight
       WHEN weight <= slap_weight THEN slap_weight
       ELSE 0
       END AS other_weight
FROM 
  (SELECT i.weight, IFNULL(r.weight, 0) as rate_weight, IFNULL(rs.weight, 0) as slap_weight
   FROM invoice I
   LEFT JOIN rate r ON r.invoice_no = i.invoice_no AND minimum_wgt <= 15
   LEFT JOIN rate_slap rs ON rs.invoice_no = i.invoice_no AND slap_weight <= 15
   WHERE customer_name = 1007
     AND destination_name = 3
     AND service_type = 1
     AND shipment_type = 'D'
     AND payment_mode = 'CASH')

我选择 0 作为 CASE 的默认值，也许它应该是发票的重量。 您需要调整表名，我使用了名称的简短版本