[MySQL练习] 查询两个表的差集（两种方法）

select st.* from student st 
inner join score sc on sc.s_id = st.s_id
inner join course c on c.c_id=sc.c_id and c.c_id="01"
where st.s_id not in (
select st2.s_id from student st2 
inner join score sc2 on sc2.s_id = st2.s_id
inner join course c2 on c2.c_id=sc2.c_id and c2.c_id="02"
)

SELECT t1.*
FROM student t1  
JOIN (SELECT s_id    
      FROM score 
      WHERE c_id =01 and s_id NOT in (SELECT s_id                                                    
                                      FROM score                                                                 
                                      WHERE c_id =02)) t2 
ON t1.s_id = t2.s_id                                      

SELECT t1.*
FROM student t1 JOIN 
(SELECT t1.s_id
FROM (SELECT s_id,s_score    
FROM score 
WHERE c_id =01) t1 
LEFT JOIN 
(SELECT s_id,s_score                                                                
FROM score 
WHERE c_id =02) t2
ON t1.s_id = t2.s_id 
WHERE t2.s_score IS NULL) t2 
ON t1.s_id = t2.s_id