MySQL JOIN：多个字段同名

Question

我不是SQL的专业人士，但我正在使用以下SELECT：

SELECT 
        certificate.id, 
        certificate.date_created,
        certificate.date_approved,
        certificate.notes,
        certificate.id_user_student,
        certificate.id_user_exm,
        certificate.id_user_eval,

        user.name AS student_name,
        user.name AS exm_name,
        user.name AS eval_name

        FROM certificate
        LEFT JOIN 
            user ON certificate.id_user_student = user.id AND
                    certificate.id_user_exm = user.id AND
                    certificate.id_user_eval = user.id

我的意见是能够将表name和user中的JOIN列放入certificate表中以放置所有用户ID字段。

在表格certificate中，id_user_student，id_user_exm，id_user_eval列包含表user上可用的用户ID，我想在结果集。

我当前的查询仅适用于第一个结果。谁能告诉我怎么解决这个问题？

谢谢！

Answer 1

您需要三个连接操作，每个“查找”基于ID的名称。您需要三个对用户表的引用，每个引用一个外键引用，例如：

SELECT c.id
     , c.date_created
     , c.date_approved
     , c.notes
     , c.id_user_student
     , c.id_user_exm
     , c.id_user_eval
     , s.name AS student_name
     , e.name AS exm_name
     , v.name AS eval_name
  FROM certificate c
  LEFT
  JOIN user s ON s.id = c.id_user_student
  LEFT
  JOIN user e ON e.id = c.id_user_exm
  LEFT
  JOIN user v ON v.id = c.id_user_eval