都不在了，在和「=」操作符SQL

Question

CARS(CCODE,ADDRESS,CITY,COLOR) 
CARS_CONTRACT(CON_CODE,ST_dATE,END_dATE,PNAME,MONTHLYPRICE,CCODE) 

發現CCODE和地址與城市=「新約克」的這montlyprice已經馬麗娟超過500 EVRO以及其中超過7個合同已簽訂，所以我代碼是

我的代碼..

select ccode,address 
from cars c,cars_contract cd 
where c.ccode=cd.ccode and city='new-york' 
and ccode not in(select ccode from cars_contract where monthlyprice<500 
group by ccode,address 
having count(*)>7 

我的問題是我可以用

這

替換上面的代碼3210

select ccode,address 
from cars c,cars_contract cd 
where c.ccode=cd.ccode and city='new-york' 
and monthlyprice>500 
group by ccode,address 
having count(*)>7 

還是這個？ （具體我一定要指定內部條款加入條件？）

select ccode,address 
from cars c,cars_contract cd 
where c.ccode=cd.ccode and city='new-york' 
and ccode in(select ccode from cars_contract where monthlyprice>500) 
group by ccode,address 
having count(*)>7 

Answer 1

你不需要額外的子查詢 - 只使用ANSI加入，而不是隱含的完全限定的所有列，以確保CCODE使用不含糊，即：

SELECT c.ccode, c.address 
FROM cars c 
    INNER JOIN cars_contract cd ON c.ccode = cd.ccode 
WHERE c.city = 'new-york' 
AND cd.monthlyprice > 500 
GROUP BY c.ccode, c.address 
HAVING COUNT(*) > 7;