OCP-1Z0-051-题目解析-第11题

11. View the Exhibit and examine the structure of the PRODUCTS table.
All products have a list price. 
You issue the following command to display the total price of each product after a discount of 25% and a

tax of 15% are  applied on it. Freight charges of $100 have to be applied to all the products.

SQL>SELECT prod_name, prod_list_price -(prod_list_price*(25/100))                 
+(prod_list_price -(prod_list_price*(25/100))*(15/100))+100                                 
AS "TOTAL PRICE" 
FROM products; 

What would be the outcome if all the parentheses are removed from the above statement?

 

A. It produces a syntax error.
B. The result remains unchanged. 
C. The total price value would be lower than the correct value. 
D. The total price value would be higher than the correct value.

 

Answer: B

题目解析：

题目的意思是：表中产品的价格降价25%后，加上税金15%，再加上运费100后产品的新价格。题目给出了产品新价格的sql语句，

问，假设把该sql语句的括号都去了，结果会如何？

这题也是考表达式的运算顺序

原sql运行结果

SELECT prod_name, prod_list_price -(prod_list_price*(25/100))                    
   +(prod_list_price -(prod_list_price*(25/100))*(15/100))+100                                    
  AS "TOTAL PRICE"   
  FROM products where rownum<10;   
  
PROD_NAME                         TOTAL PRICE  
--------------------------------- -----------  
VRAM - 64 MB                      577.7875
CPU D300                          272.9625
CPU D400                          310.6375
CPU D600                           404.825
GP 1024x768                        233.575
GP 1280x1024                       267.825
GP 800x600                           182.2
MB - S300                         194.1875
MB - S450                          213.025

去括号后sql运行结果

SELECT prod_name, prod_list_price -prod_list_price*25/100                    
   +prod_list_price -prod_list_price*25/100*15/100+100                                    
  AS "TOTAL PRICE"   
  FROM products where rownum<10;   
  
PROD_NAME                         TOTAL PRICE  
--------------------------------- -----------  
VRAM - 64 MB                      577.7875
CPU D300                          272.9625
CPU D400                          310.6375
CPU D600                           404.825
GP 1024x768                        233.575
GP 1280x1024                       267.825
GP 800x600                           182.2
MB - S300                         194.1875
MB - S450                          213.025

结果是一样的，所以选B

事实上这道题，题目给的sql的括号位置应该错了，正确的应该是 这种

 SELECT prod_name, prod_list_price -(prod_list_price*(25/100)) 
+(prod_list_price -(prod_list_price*(25/100)))*(15/100)+100 
AS "TOTAL PRICE" 
FROM products;

假设是题目给的括号位置，能够測试下

select 100 -(100*(25/100))+(100 -(100*(25/100))*(15/100))+100  from dual;

 

100-(100*(25/100))+(100-(100*(25/100))*(15/100))+100
----------------------------------------------------
271.25

结果是271.25了，显示和题目说的不一致。