mysql - 需要有关 SQL 查询的帮助

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，以便我只选择同时具有登录角色 1 和 2 (loginrole.id) 的员工/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，这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，找到具有以下任一条件的员工:

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)