sql - 没有附加或连接的名字和姓氏的 SQL 条件

Question

您有 2 个表 Customers 和 Blacklist，均包含 firstname 和 lastname 列。

如何找到好的客户？请注意，由于字符限制，我不能将姓氏附加或连接到名字（反之亦然）。

我认为左连接会起作用。请确认。

select c.lastname,c.firstname
from Curtomers c
left join Blacklist b
ON (c.lastname = b.lastname
AND c.firstname = b.lastname)
where b.firstname is null
and b.lastname is null

Answer 1

SELECT    c.*
FROM      Customer c
WHERE NOT EXISTS (
  SELECT  *
  FROM    Blacklist b
  WHERE   c.firstname = b.firstname
    AND   c.lastname = b.lastname
)

我假设您是在推断“好客户”不在blacklist表中？另外，我不知道您使用的是什么 dbms。

Answer 2

SELECT * 
FROM Customers C
LEFT OUTER JOIN Blacklist BL ON C.firstname = BL.firstname AND
                                C.lastname = BL.lastname   
WHERE BL.firstname IS NULL

Answer 3

怎么样

SELECT c.*
FROM Customers c LEFT JOIN
BlackList b ON c.FirstName = b.FirstName AND c.LastName = b.LastName
WHERE b.FirstName IS NULL

看看这个漂亮的 JOINS 视觉表示

JOIN 简介 – JOIN 基础

Answer 4

select *
from customers
minus
select *
from blacklist