mysql - Mysql Left Join 不返回所有值

Question

我有一个简单的 mysql 查询可以正常工作，但它不会返回所有值。当我单独使用左连接表时，所有值都会返回，但是当我添加其他表时，只有那些都是“=”的表才会返回一个值。这是查询：

SELECT 

d.flight_no   , b.arrival_flight

FROM  
jtl_booking_transfer_details                    AS      b
LEFT  JOIN jtl_flight_info                      AS      d      
       ON  (d.flight_no      b.arrival_flight),

jtl_booking_master                                     a,
jtl_hotels                                             c,                                                               
jtl_airlines                                           e


WHERE 

a.voucher_number                             =        b.voucher_number             AND 
b.hotel_id                                   =        c.hotel_id                   AND
e.airline_code                               =        d.airline_code              

Answer 1

使用相同的语法获取所有表（更易于阅读：JOIN for ... 连接表，WHERE 子句用于其他谓词）

SELECT 
d.flight_no   , b.arrival_flight

FROM  
jtl_booking_transfer_details b
LEFT JOIN jtl_flight_info d      
   ON  d.flight_no = b.arrival_flight
LEFT JOIN  jtl_booking_master a 
   ON a.voucher_number = b.voucher_number
LEFT JOIN jtl_hotels c 
   ON b.hotel_id = c.hotel_id
LEFT JOIN jtl_airlines  e 
   ON  e.airline_code = d.airline_code