Question

表A

    > - Product#|Customer|state|Type   
      Glasses |mr. Xyz | MN |Instore    
      Glasses |mr. abc | MN |Instore    
  perishables|mr. abc12| TN |Instore 
 N-perishables|mr. abc122| GN |Instore

表B

> - Product#|Name|state|Type   
  Glasses |mr. fff | MN |online    
  Glasses |mr. abc | MN |online    
perishables|mr. abc12 | TN |online 
 Non-perishables|mr. abc122 | GN |online

`

尝试创建新列，然后进行比较？条件是，如果类型为店内，则它们永远不是新客户；如果在线，则只有在店内类型中不存在记录的情况下，他们才可以为新客户。

o / p

Type|customer| New Customer?
Instore|mr. Xyz  |No
Instore|mr. abc  |No
Instore|mr. abc12|No
Instore|mr. abc122|No
Online| mr.fff    |Yes -"as it's record is not available  in-store type, hence it will be labelled as new customer"

尝试查询：

select 
       `Customer`, 
    CASE
    WHEN `customer` in (select `Customer` from `Table B`)  THEN 'Yes'
    ELSE 'NO'
END AS 'new customer'
FROM Table A`

Answer 1

使用连接而不是子查询：

SELECT 
    COALESCE(a."Type", b."Type") as type,
    COALESCE(a."Customer", b."Name") as customer,
    CASE
      WHEN b."Type" = 'online' AND a."Customer" IS NULL THEN 'Yes'
      ELSE 'No'
    END AS new_customer
FROM "Table_B" b
FULL JOIN "Table_A" a
ON a."Customer" = b."Name";

顺便说一句，两个表中的数据似乎都是重复的，您可能需要重新考虑自己的模式。

Answer 2

您可以将LEFT和RIGHT联接与UNION结合使用：

SELECT coalesce(type_a ,type_b) as type,
       coalesce(customer_a,customer_b) as customer, 
       case when type_a is null then 'Yes' else 'No' end as New_Customer
  FROM
  ( 
    SELECT a.type as type_a,a.customer as customer_a, 
           b.type as type_b,b.customer as customer_b
      FROM TableA a
      LEFT JOIN TableB b
        ON a.Customer=b.Customer
     UNION
    SELECT a.type as type_a,a.customer as customer_a, 
           b.type as type_b,b.customer as customer_b
      FROM TableA a
      RIGHT JOIN TableB b
         ON a.Customer=b.Customer
   ) q

Demo

Answer 3

您需要一个LEFT JOIN中的一个TableB到TableA和一个CASE表达式，它们将返回您想要的结果：

select
  b.Product,
  case when a.Product is null then 'YES' else 'NO' end as `new customer`
from TableB as b left join TableA as a
on b.Product = a.Product

请参见demo。
结果：

| Product | new customer |
| ------- | ------------ |
| 11120   | NO           |
| 11121   | NO           |
| 11122   | NO           |
| 11123   | NO           |
| 11124   | YES          |

创建新列和比较

3 个答案: