查询不属于特定组的用户？ （想使用EXCEPT，但MySQL似乎不支持它）

Question

我在用户和组之间有多对多的关系：

CREATE TABLE IF NOT EXISTS `SecurityIdentifiers` (
  `Guid` char(36) NOT NULL,
  PRIMARY KEY  (`Guid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `CaseIdUsers` (
  `Sid` char(36) NOT NULL,
  `Acl` int(11) NOT NULL,
  `FirstName` varchar(45) NOT NULL,
  `LastName` varchar(45) NOT NULL,
  `CaseID` varchar(8) NOT NULL,
  PRIMARY KEY  (`Sid`),
  UNIQUE KEY `CaseID_UNIQUE` (`CaseID`),
  KEY `fk_CaseIDUsers_AccessControlLists1` (`Acl`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `GroupMembers` (
  `User` char(36) NOT NULL,
  `Group` char(36) NOT NULL,
  PRIMARY KEY  (`User`,`Group`),
  KEY `fk_Groups_has_SecurityIdentifiers_SecurityIdentifiers1` (`User`),
  KEY `fk_Groups_has_SecurityIdentifiers_Groups1` (`Group`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `Groups` (
  `Sid` char(36) NOT NULL,
  `Acl` int(11) NOT NULL,
  `Name` varchar(45) NOT NULL,
  `Description` varchar(255) NOT NULL,
  PRIMARY KEY  (`Sid`),
  UNIQUE KEY `Name_UNIQUE` (`Name`),
  KEY `fk_Groups_Access Control Lists1` (`Acl`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

我需要找到不属于特定组的所有用户。我想做类似的事情：

SELECT CaseId FROM CaseIdUsers
EXCEPT
SELECT CaseId FROM CaseIdUsers
JOIN GroupMembers ON GroupMembers.User = CaseIdUsers.Sid
JOIN Groups ON GroupMembers.Group = Groups.Sid
WHERE Groups.Name = 'MyGroupName'

但 MySQL 不支持 EXCEPT。我现在该怎么办？

Answer 1

您可以使用 NOT IN() ，或 < ;> ANY()

SELECT CaseId
FROM CaseIdUsers
WHERE CaseID NOT IN (
  SELECT CaseId 
  FROM CaseIdUsers
    JOIN GroupMembers ON GroupMembers.User = CaseIdUsers.Sid
    JOIN Groups ON GroupMembers.Group = Groups.Sid
  WHERE Groups.Name = 'MyGroupName'
)

或者，您可以将 LEFT JOIN 与 GROUP BY 结合使用

SELECT CaseId 
FROM CaseIdUsers
  LEFT JOIN GroupMembers ON GroupMembers.User = CaseIdUsers.Sid
  LEFT JOIN Groups ON GroupMembers.Group = Groups.Sid
    AND Groups.Name = 'MyGroupName'
HAVING COUNT(Groups.Sid) = 0