遇到錯誤時做的「選擇」與「NOT EXISTS」和「除」

Question

有人可以幫助我，爲什麼是這個查詢，

select Fname, Lname from EMPLOYEE where not exists ((select Pnumber from PROJECT where Dnum=5) except (select Pno from WORKS_ON where EMPLOYEE.Ssn=Essn)); 

給我的錯誤信息，

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'except (select Pno from WORKS_ON where EMPLOYEE.Ssn=Essn))' at line 1 

它混淆了我coz

select Pnumber from PROJECT where Dnum=5 

不給我任何錯誤信息。我在一本關於製作大學數據庫的書中作爲例子。

mysql> show columns from EMPLOYEE; 
+-----------+---------------+------+-----+---------+-------+ 
| Field  | Type   | Null | Key | Default | Extra | 
+-----------+---------------+------+-----+---------+-------+ 
| Fname  | varchar(15) | NO |  | NULL |  | 
| Minit  | char(1)  | YES |  | NULL |  | 
| Lname  | varchar(15) | NO |  | NULL |  | 
| Ssn  | char(9)  | NO | PRI | NULL |  | 
| Bdate  | date   | YES |  | NULL |  | 
| Address | varchar(30) | YES |  | NULL |  | 
| Sex  | char(1)  | YES |  | NULL |  | 
| Salary | decimal(10,2) | YES |  | NULL |  | 
| Super_ssn | char(9)  | YES | MUL | NULL |  | 
| Dno  | int(11)  | NO |  | NULL |  | 
+-----------+---------------+------+-----+---------+-------+ 

mysql> show columns from PROJECT; 
+-----------+-------------+------+-----+---------+-------+ 
| Field  | Type  | Null | Key | Default | Extra | 
+-----------+-------------+------+-----+---------+-------+ 
| Pname  | varchar(15) | NO | UNI | NULL |  | 
| Pnumber | int(11)  | NO | PRI | NULL |  | 
| Plocation | varchar(15) | YES |  | NULL |  | 
| Dnum  | int(11)  | NO | MUL | NULL |  | 
+-----------+-------------+------+-----+---------+-------+ 

mysql> show columns from WORKS_ON; 
+-------+--------------+------+-----+---------+-------+ 
| Field | Type   | Null | Key | Default | Extra | 
+-------+--------------+------+-----+---------+-------+ 
| Essn | char(9)  | NO | PRI | NULL |  | 
| Pno | int(11)  | NO | PRI | NULL |  | 
| Hours | decimal(3,1) | NO |  | NULL |  | 
+-------+--------------+------+-----+---------+-------+ 

Answer 1

你可以改變你這樣的查詢

select 
    Fname, 
    Lname 
from EMPLOYEE 
where not exists(select 
      Pnumber 
     from PROJECT 
     where Dnum = 5) 
    OR EMPLOYEE.Ssn IN(select 
       Pno 
        from WORKS_ON 
        where EMPLOYEE.Ssn = Essn)