Some Advanced SQL Quiz Answers

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Some Advanced SQL Quiz Answers

Question 1)

Which statements correctly describe a VIEW ? (Choose all that apply.) 

• A view holds its data until it is TRUNCATED.
• A view can be used to hide confidential data. 
• A view is defined by a SELECT statement within a CREATE statement 
• A view contains no data until it is queried. 

Question 2)

True/False: The CASE expression can be used in place of SQL’s IF/THEN/ELSE function. 

• False
• True

Question 3)

Which statements correctly describe a UNION ? (Choose all that apply.) 

• Combining data from two tables with a UNION yields the same result as an INNER JOIN of those two tables. 
• Two answer sets joined in a UNION must have the same number of columns. 
• Two answer sets joined in a UNION must have the same number of rows. 
• Corresponding columns of answer sets joined by a UNION must have the same data type. 

Question 4)

Which statements are true of the SQL IDENTITY constraint ? (Choose all that apply.) 

• The SEQUENCE associated with a SQL IDENTITY controls the next number to be assigned, and the increment used for generating each new number.
• The SQL IDENTITY provides a convenient means of creating a surrogate key. 
• The SQL IDENTITY includes logic to handle “collisions” if duplicate numbers are generated. 
• The SQL IDENTITY provides a unique value that can be used as a primary key. 

Question 5)

True/False: The IDENTITY constraint is use in both PostgreSQL and MySQL. 

• True
• False