Php 连接相同表的多行

我试图从一个表中提取两组不同的数据。不过，我不太确定如何处理这个问题。这是当前设置的表（相关）

通过使用以下查询，我可以使收件人与姓名匹配：

SELECT 
   usr.username, usr.id,  sl.recipient, sl.given_by, 
   sl.time, sl.experation, sl.points, sl.reason
FROM 
    DD_users AS usr
LEFT JOIN
    DD_schittlist AS sl
ON (sl.recipient = usr.id)       
GROUP BY
        usr.id
ORDER BY 
        sl.points DESC,
        usr.username

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这将使收件人72与用户72相匹配，但我还想使gived by 1显示admin，gived by 4显示为user4。

您需要针对

DD\u users

表加入两次，一次用于

id

，另一次用于

gived\u by

。每个都有自己的别名，必须在

SELECT

列表中使用别名来消除歧义（

usr，给定的

）

尝试以下操作：（您只需为DD_users表的第二个引用添加别名，并添加第二个join语句，然后在select语句中引用别名用户名列。）

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为什么左外连接？从这个模型看来，这两个表之间应该始终存在链接。除非，你打算允许删除数据吗？我从一个模型中使用它，该模型不是所有的值都有链接，但我希望以任何方式显示它们。我不是SQL中所有连接的专家，所以如果它能工作，我就不用管它了。谢谢。没想到会像做第二个别名那么简单。

SELECT 
   usr.username, usr.id,  sl.recipient, sl.given_by, 
   sl.time, sl.experation, sl.points, sl.reason
FROM 
    DD_users AS usr
LEFT JOIN
    DD_schittlist AS sl
ON (sl.recipient = usr.id)       
GROUP BY
        usr.id
ORDER BY 
        sl.points DESC,
        usr.username

  SELECT 
    /* The original username you already had */
    usr.username, 
    usr.id,  
    sl.recipient, 
    sl.given_by, 
    /* The given_by username from the given alias table */
    /* Be sure to alias this column here as well to differentiate them in the client */
    given.username AS given_by_username,
    sl.time, 
    sl.experation, 
    sl.points, 
    sl.reason
  FROM 
    DD_users AS usr
    /* First join you already had between id and recipient */
    LEFT JOIN DD_schittlist AS sl ON (sl.recipient = usr.id)       
    /* A second LEFT JOIN between DD_shittlist and DD_users as given */
    /* (LEFT JOIN permits nulls in DD_shittlist.given_by) */
    LEFT JOIN DD_users AS given ON sl.given_by = given.id
  GROUP BY
    usr.id
  ORDER BY 
    sl.points DESC,
    usr.username

  SELECT 
    usr.username, usr.id,  sl.recipient, sl.given_by, usr2.username, sl.time, sl.experation, sl.points, sl.reason
  FROM 
    DD_users AS usr
  LEFT JOIN DD_schittlist AS sl  ON (sl.recipient = usr.id)    
  JOIN DD_users as usr2 ON (usr2.id = sl.given_by)   
  GROUP BY
    usr.id
  ORDER BY 
    sl.points DESC,
    usr.username