Reviewing Table Creation Basics - Quiz Explanation

The correct answers are indicated below, along with text that explains the correct answers.
 
1. Which one of these is syntactically correct?
Please select the best answer.
  A. CREATE TABLE auction COLS(auction_id NUMBER, start_time DATE, stop_time DATE)
  B. CREATE TABLE (auction_id NUMBER, start_time DATE, stop_time DATE)
  C. CREATE TABLE auction (auction_id NUMBER, start_time DATE, stop_time DATE)
  D. CREATE TABLE AUCTION (auction_id NUMBER, start_time DATE, stop_time)
  C is correct.
Answer A includes the superfluous word COLS. Answer B is missing a name for the table. Answer D is missing a datatype for the final column in the column list.

2. You must define a column holding up to 800 English language characters. The best datatype for the column is:
Please select the best answer.
  A. CHAR(800)
  B. VARCHAR2(800)
  C. CLOB
  D. NVARCHAR2(800)
  The correct answer is B.
The best answer is B, since the VARCHAR2 datatype will not waste space if the column is less than 800 characters, as the CHAR(800) datatype would. The CLOB will work, but since its extra space allowance is not needed, it is not the best datatype. The NVARCHAR2 datatype can hold English characters, but there is no need to use it, since the VARCHAR2 will also hold the characters.

3. You want to store a string of 8,000 Japanese characters in a column. You would define the column with a datatype of:
Please select the best answer.
  A. NCHAR(8000)
  B. NVARCHAR2(8000)
  C. NLOB
  D. CLOB
  The correct answer is C.
For this task, you have to use a datatype that can accept NLS characters. Because you are storing more than 2,000 NLS characters, you cannot use NCHAR datatype. Because you are storing more than 4,000 Japanese characters, you cannot use NVARCHAR2 datatype. And because you are storing Japanese characters, you cannot use the CLOB datatype. The NLOB datatype accepts up to 4 megabytes of NLS characters, and therefore the correct answer is C.