Question

您有2个表客户和黑名单，都有列名字和姓氏。

您如何找到好客户？请注意，由于字符限制，我无法将姓氏附加或连接到名字（反之亦然）。

我认为左连接可行。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
)

我认为你推断一个不在blacklist表中的“好顾客”？另外，我不知道你正在使用什么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JOINS的这个漂亮的视觉表现

Introduction to JOINs – Basic of JOINs

Answer 4

select *
from customers
minus
select *
from blacklist

firstname和lastname上的SQL条件没有append或concat

4 个答案: