13.View the Exhibit and examine the structure of the PRODUCTS table.

13.View the Exhibit and examine the structure of the PRODUCTS table.

You need to generate a report in the following format:

CATEGORIES

5MP Digital Photo Camera's category is Photo

Y Box's category is Electronics

Envoy Ambassador's category is Hardware



Which two queries would give the required output? (Choose two.)

A.SELECT prod_name q'''s category is ' prod_category CATEGORIES FROM products;

B.SELECT prod_name q'['s ]'category is ' prod_category CATEGORIES FROM products;

C.SELECT prod_name q'\'s\' ' category is ' prod_category CATEGORIES FROM products;

D.SELECT prod_name q'<'s >' 'category is ' prod_category CATEGORIES FROM products;

答案：CD

解析：这道题考察的是q前缀，在oracle中表示一个单引号或者其他特殊字符，需要'',因此如果表示's，需要''s,然后把它括起来的话

就需要如下，这种方式

SQL> select '''s' from dual;

''

--

's

oracle为了处理简便，出现了q前缀，也就是一个q然后更一个单引号，然后一个任意字符，然后是你要显示的内容，最后对应的任意字符和单引号，比如下面这个

SQL> select q'{a'a}',q'| b'b|',q'[ c'c ]',q'\ d'd\',q'a e'ea',q'( f'f)' from dual;

Q'{ Q'|B Q'[C' Q'\D Q'AE Q'(F

--- ---- ----- ---- ---- ----

a'a b'b c'c d'd e'e f'f

这里需要注意，如果使用括号的话，应该是左右匹配，不能是相同的比如(){}[]，中文的测试不行

A：错误，q'''s category is ' 这个q''是开头，然后没有找到结束的''

B：错误，q'['s ]'category is '这里应该改成q'['s category is ]'

C：正确,q'\'s\' ' category is '这里的连接都没有使用||,就q前缀来说是正确的，因为q'\'s\'表示's,' category is '表示category is，因此我觉得这里其实应该是

q'\'s\'||' category is '

D：正确，q'<'s >' 'category is '同C，我觉得应该是q'<'s >'||'category is '