SQL測驗選擇/子查詢

Question

請參閱給定的SQL語句。

1. Select SPNAME 
2. FROM SALESPERSON 
3. Where SPNUM= 
4. FROM CUSTOMER 
5. WHERE CUSTNUM=20900); 

在第4行開頭的子查詢中缺少什麼？

(SELECT SPNUM 
(SPNUM 
(Subquery SPNUM 
(FIND SPNUM 

Answer 1

我想查詢應該是WHERE SPNUM = ...或WHERE SPNUM IN ...後跟一個子查詢。爲了安全起見，我們可以在子查詢返回多條記錄的情況下使用WHERE SPNUM IN ...。

SELECT SPNAME 
FROM SALESPERSON 
WHERE SPNUM IN (SELECT SPNUM FROM CUSTOMER WHERE CUSTNUM = 20900)