MySQL:选择连接表匹配所有值的记录

Question

我试图找到所有具有多种技能的员工。以下是表格:

CREATE TABLE IF NOT EXISTS `Employee` (
  `ID` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `Name` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ;
INSERT INTO `Employee` (`ID`, `Name`, `Region_ID`) VALUES (1, 'Fred Flintstone'), (2, 'Barney Rubble');

CREATE TABLE IF NOT EXISTS `Skill` (
  `ID` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `Name` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ;
INSERT INTO `Skill` (`ID`, `Name`) VALUES (1, 'PHP'), (2, 'JQuery');

CREATE TABLE IF NOT EXISTS `Emp_Skills` (
  `ID` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `Emp_ID` bigint(20) unsigned NOT NULL DEFAULT '0',
  `Skill_ID` bigint(20) unsigned NOT NULL DEFAULT '0',
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=5 ;
INSERT INTO `Emp_Skills` (`ID`, `Emp_ID`, `Skill_ID`) VALUES (1, 1, 1), (2, 1, 2), (3, 2, 1);

这是我目前的查询:

SELECT DISTINCT(em.ID), em.Name 
FROM Employee em 
INNER JOIN Emp_Skills es ON es.Emp_ID = em.ID
WHERE es.Skill_ID IN ('1', '2')

这会返回两个员工，但是，我需要找到具有这两种技能(ID 1 和 2)的员工。

有什么想法吗？谢谢

Answer 1

这样做就可以了:

SELECT EmpId, Name
FROM
(
   SELECT em.ID as EmpId, em.Name, es.ID as SkillID 
   FROM Employee em 
   INNER JOIN Emp_Skills es ON es.Emp_ID = em.ID
   WHERE es.Skill_ID IN ('1', '2')
 ) X
GROUP BY EmpID, Name
HAVING COUNT(DISTINCT SkillID) = 2;

Fiddle here:

不同是为了防止同一员工具有两次列出的技能。

感谢提供测试数据。