Question

当前查询

SELECT *
FROM employee AS E
INNER JOIN credential AS C ON (C.id = E.credentialId)
LEFT JOIN person AS P ON (C.personId = P.id)

我想修改此查询，以便我只选择具有loginroles 1和2（loginrole.id）的employees /凭证。

相关表格

loginrole
    id
    name
credential_has_loginrole
    id
    credentialId
    loginroleId

Answer 1

您可以加入子查询，该子查询将返回具有两个登录角色的凭证ID。

SELECT E.*, C.*, P.*
FROM employee AS E
  INNER JOIN (
      SELECT credentialId
      FROM credential_has_loginrole
      WHERE loginroleId IN (1,2)
      GROUP BY credentialId
      HAVING COUNT(DISTINCT loginroleId) = 2
    ) g ON E.credentialId = g.credentialId
  INNER JOIN credential AS C ON (C.id = E.credentialId)
  LEFT JOIN person AS P ON (C.personId = P.id)

更新：根据评论，查找员工或：或

SELECT E.*, C.*, P.*
FROM employee AS E
  INNER JOIN (
      SELECT credentialId
      FROM credential_has_loginrole
      WHERE loginroleId IN (1,2)
      GROUP BY credentialId
    ) g ON E.credentialId = g.credentialId
  INNER JOIN credential AS C ON (C.id = E.credentialId)
  LEFT JOIN person AS P ON (C.personId = P.id)

或者，您可以将JOIN与DISTINCT一起使用：

SELECT DISTINCT E.*, C.*, P.*
FROM employee AS E
  INNER JOIN credential AS C ON (C.id = E.credentialId)
  INNER JOIN credential_has_loginrole chr
    ON E.credentialId = chr.credentialId
      AND chr.loginroleId IN (1,2)
  LEFT JOIN person AS P ON (C.personId = P.id)

Answer 2

Scrum Meister的回答是正确的。您也可以使用2个连接树：

    SELECT *
    FROM employee AS E
    INNER JOIN credential AS c 
        INNER JOIN credential_has_loginrole chl0 ON (c0.id=chl0.credentialId AND chl0.loginroleId=1)
        INNER JOIN credential_has_loginrole chl1 ON (c0.id=chl1.credentialId AND chl1.loginroleId=2)
    ON (c.id = E.credentialId)

需要SQL查询的帮助

2 个答案: