Mysql 在查询中使用except时出错

此查询可用于：

mysql> SELECT s.sno FROM students s;  
+------+  
| sno  |   
+------+   
|    1 |   
|    2 |   
|    3 |   
|    4 |   
|    5 |    
|    6 |    
|    7 |   
|    8 |   
|    9 |   
|   10 |   
+------+   
10 rows in set (0.00 sec)  

此查询也适用于以下情况：

mysql> SELECT t.sno FROM take t WHERE t.cno = 'CS112';  
+------+  
| sno  |  
+------+  
|    1 |  
|    2 |  
|    3 |  
|    4 |  
+------+   
4 rows in set (0.00 sec)  

但这个问题：

SELECT s.sno FROM students s    
EXCEPT    
SELECT t.sno FROM take t WHERE t.cno = 'CS112';  

失败，错误为：

mysql> SELECT s.sno FROM students s  
    -> EXCEPT  
    -> SELECT t.sno FROM take t WHERE t.cno = 'CS112';  
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 n   
ear 'EXCEPT   
SELECT t.sno FROM take t WHERE t.cno = 'CS112'' at line 2 

---

我做错了什么？

我不相信MySQL除了语法之外还支持其他功能。尝试使用

不在

或

左连接

：

SELECT s.sno 
FROM students s    
WHERE s.sno NOT IN 
(
    SELECT t.sno 
    FROM take t 
    WHERE t.cno = 'CS112'
);

或

更新

我模拟了您的数据，它正确地返回5到10：

create temporary table temp_students (sno int)

insert into temp_students values (1)
insert into temp_students values (2)
insert into temp_students values (3)
insert into temp_students values (4)
insert into temp_students values (5)
insert into temp_students values (6)
insert into temp_students values (7)
insert into temp_students values (8)
insert into temp_students values (9)
insert into temp_students values (10)

create temporary table temp_take (sno int, cno varchar(50))

insert into temp_take values (1, 'CS112')
insert into temp_take values (2, 'CS112')
insert into temp_take values (3, 'CS112')
insert into temp_take values (4, 'CS112')

SELECT s.sno 
FROM temp_students s    
        LEFT JOIN temp_take t ON s.sno = t.sno
WHERE IFNULL(t.cno, '') != 'CS112'

---

除了语法，我不相信MySQL支持。尝试使用

不在

或

左连接

：

SELECT s.sno 
FROM students s    
WHERE s.sno NOT IN 
(
    SELECT t.sno 
    FROM take t 
    WHERE t.cno = 'CS112'
);

或

更新

我模拟了您的数据，它正确地返回5到10：

create temporary table temp_students (sno int)

insert into temp_students values (1)
insert into temp_students values (2)
insert into temp_students values (3)
insert into temp_students values (4)
insert into temp_students values (5)
insert into temp_students values (6)
insert into temp_students values (7)
insert into temp_students values (8)
insert into temp_students values (9)
insert into temp_students values (10)

create temporary table temp_take (sno int, cno varchar(50))

insert into temp_take values (1, 'CS112')
insert into temp_take values (2, 'CS112')
insert into temp_take values (3, 'CS112')
insert into temp_take values (4, 'CS112')

SELECT s.sno 
FROM temp_students s    
        LEFT JOIN temp_take t ON s.sno = t.sno
WHERE IFNULL(t.cno, '') != 'CS112'

试试这个

SELECT s.sno FROM students s
LEFT JOIN take t ON t.sno = s.sno AND t.cno = 'CS112' 
WHERE t.sno IS NULL;

试试这个

SELECT s.sno FROM students s
LEFT JOIN take t ON t.sno = s.sno AND t.cno = 'CS112' 
WHERE t.sno IS NULL;

查询：

SELECT s.sno 
FROM students s
WHERE NOT EXISTS (SELECT 0 
                  FROM take t 
                  WHERE t.sno = s.sno 
                  AND t.cno = 'CS112') 

查询：

SELECT s.sno 
FROM students s
WHERE NOT EXISTS (SELECT 0 
                  FROM take t 
                  WHERE t.sno = s.sno 
                  AND t.cno = 'CS112') 

---

除了，您不支持

，这是对的。但是，您的备选方案没有产生正确的结果。您发布的查询没有返回该结果。我模拟了您的数据并返回了5-10。请参阅修改后的答案。关于除

之外不支持

，您是对的。但是，您的备选方案没有产生正确的结果。您发布的查询没有返回该结果。我模拟了您的数据并返回了5-10。请参阅修改后的答案。这是最佳答案，因为它也适用于多个字段。这是最佳答案，因为它也适用于多个字段