SQL在查询多个表时组合来自同一个表的多个列

Question

我有三个表格，如下所示。

1. usedetails [ID,first_name,last_name,telephone,email]

2. 地址[ID,街道号码,街道名称,城镇,县,邮编,用户详情ID]

3. 预订 [ID,customerID,pickup_address_id,dropoff_address_id,charge,no_of_passenger]

地址表包含两种类型的地址，即pickoff 和dropoff。我想将两个地址中的每一个显示为一个字符串。以下是我的查询。

query = "SELECT A.streetnumber,
                        A.streetname,
                        A.town,
                        A.postcode
                    AS pickup_point
                        AB.streetnumber,
                        AB.streetname,
                        AB.town,
                        AB.postcode
                    AS  dropoff_point
                        UD.first_name,
                        UD.last_name,
                        UD.telephone,
                        UD.email
                    FROM userdetails UD 
                    INNER JOIN booking B
                    ON B.customerID = UD.ID
                    INNER JOIN address A
                    ON B.pickup_address_id = A.ID
                    INNER JOIN address AB
                    ON AB.drop_off_address_id = A.ID
                    WHERE UD.ID = A.userdetailsID OR UD.ID = AB.userdetailsID";

Answer 1

试试CONCAT函数：

SELECT CONCAT(A.streetnumber,
              ' ',
              A.streetname,
              ' ',
              A.town,
              ' ',
              A.postcode) AS pickup_point, ...

或 CONCAT_WS 函数将分隔符作为第一个参数传递：

SELECT CONCAT_WS(' ',
                 A.streetnumber,
                 A.streetname,
                 A.town,
                 A.postcode) AS pickup_point, ...