Question

我正在使用三个SQL表，并且正在使用INNER JOIN联接这些表。这是表格的概述。

CREATE TABLE `User` (
   `id` varchar(32) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
   `firstName` varchar(64) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
   `lastName` varchar(64) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
   `email` varchar(64) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
   PRIMARY KEY (`id`)                                                                       ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |


CREATE TABLE `Ownership` ( 
   `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
   `user` varchar(32) COLLATE utf8_unicode_ci NOT NULL,
   `certificate` int(10) unsigned NOT NULL,
   PRIMARY KEY (`id`),
   UNIQUE KEY `unicity` (`user`,`certificate`)                                              ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci 

CREATE TABLE `Certificate` (
   `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
   `domain` varchar(64) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
   `creationDate` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,   
   `expirationDate` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
   `type` varchar(32) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
   PRIMARY KEY (`id`)                                                                       ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8

加入表的请求如下：

select user, lastName, domain 
from Ownership 
    INNER JOIN User ON Ownership.user = User.id 
    INNER JOIN Certificate ON Ownership.certificate = Certificate.id;`

例如，我有这种类型的结果：

我想要的是只为一个域名检索一个用户，并创建一个仅在certificate.domain值不存在的情况下才能加入的例外。

MYSQL有可能吗？

谢谢

Answer 1

您需要进行预查询，以至少限定与给定域关联的某些唯一性组件。为此，请考虑一下。

import re

test_str = "[('15000042', 19)]"
result = re.sub(r"[^\w,]+", "", test_str)

if result:
    print (result)

因此，这将获得一个给定域的用户。现在，使用THAT结果获取与该域关联的用户。

select 
      C.domain,
      min( O.user ) JustOneUser 
   from 
      Certificate C
         JOIN Ownership O
            on C.ID = O.Certificate
   group by
      C.Domain

MYSQL加入三个例外表

1 个答案: