Not unique table/alias

问题:

I get the error ERROR 1066 (42000): Not unique table/alias:

I cant figure out whats wrong with it.

SELECT Project_Assigned.ProjectID, Project_Title, Account.Account_ID, Username, Access_Type
FROM Project_Assigned 
JOIN Account 
  ON Project_Assigned.AccountID = Account.Account_ID
JOIN Project
  ON Project_Assigned.ProjectID = Project.Project_ID
where Access_Type = 'Client';

回答1:

Try

    SELECT pa.ProjectID, p.Project_Title, a.Account_ID, a.Username, a.Access_Type, c.First_Name, c.Last_Name
      FROM Project_Assigned pa
INNER JOIN Account a
        ON pa.AccountID = a.Account_ID
INNER JOIN Project p
        ON pa.ProjectID = p.Project_ID
INNER JOIN Clients c
        ON a.Account_ID = c.Account_ID
     WHERE a.Access_Type = 'Client';

回答2:

 select persons.personsid,name,info.id,address
    -> from persons
    -> inner join persons on info.infoid = info.info.id;