In which case would you use a FULL OUTER JOIN?

To answer this question, the user must know the different types of joins in SQL.

• INNER JOIN: returns only matched data from both tables.
• LEFT OUTER JOIN: returns all data from the left table and matched data from the right table.
• RIGHT OUTER JOIN: returns all data from the right table and matched data from the left table.
• FULL OUTER JOIN: returns all matched and unmatched data from both tables.

Now, let's go through each option and determine whether it is a valid case to use a FULL OUTER JOIN:

A. Both tables have NULL values.

• This option is not a determining factor in deciding to use a FULL OUTER JOIN.

B. You want all unmatched data from one table.

• This option does not require a FULL OUTER JOIN, as a LEFT OUTER JOIN or RIGHT OUTER JOIN would suffice depending on which table has the unmatched data.

C. You want all matched data from both tables.

• This option requires an INNER JOIN, not a FULL OUTER JOIN.

D. You want all unmatched data from both tables.

• This option requires a FULL OUTER JOIN, as it returns all matched and unmatched data from both tables.

E. One of the tables has more data than the other.

• This option does not necessarily require a FULL OUTER JOIN, as a LEFT OUTER JOIN or RIGHT OUTER JOIN could also be used depending on which table has more data.

F. You want all matched and unmatched data from only one table.

• This option does not require a FULL OUTER JOIN, as a LEFT OUTER JOIN or RIGHT OUTER JOIN could be used depending on which table has the data.

Therefore, the correct answer is:

The Answer is: D