To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) INSTR returns the numeric position of a named character. - This option is correct. The INSTR function in SQL returns the position of a specified character or substring within a string.

Option B) NVL2 returns the first non-null expression in the expression list. - This option is incorrect. The NVL2 function in SQL returns the second expression if the first expression is not null, otherwise, it returns the third expression.

Option C) TRUNCATE rounds the column, expression, or value to n decimal places. - This option is incorrect. The TRUNCATE function in SQL is used to remove all rows from a table or a partition, not to round values.

Option D) DECODE translates an expression after comparing it to each search value. - This option is correct. The DECODE function in SQL compares an expression to each search value and returns a result based on the match.

Option E) TRIM trims the heading or trailing characters (or both) from a character string. - This option is correct. The TRIM function in SQL removes leading and trailing characters (or both) from a character string.

Option F) NULLIF compares two expressions and returns null if they are equal, or the first expression if they are not equal. - This option is correct. The NULLIF function in SQL compares two expressions and returns null if they are equal, or the first expression if they are not equal.

The four correct statements are A) INSTR, D) DECODE, E) TRIM, and F) NULLIF.

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• Wrong explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) SELECT &1, "&2" FROM &3 WHERE last_name = '&4'; This option is incorrect because it uses double quotation marks around &2, which would treat the input value as a string literal instead of a column name.

Option B) SELECT &1, '&2' FROM &3 WHERE '&last_name = '&4''; This option is incorrect because it contains syntax errors. The single quotation mark before "last_name" is misplaced, and there is an extra single quotation mark at the end.

Option C) SELECT &1, &2 FROM &3 WHERE last_name = '&4'; This option is correct because it allows user input for the columns to be displayed, the table name, and the WHERE condition. The input values &1, &2, &3, and &4 will be replaced with the user's input during runtime.

Option D) SELECT &1, '&2' FROM EMP WHERE last_name = '&4'; This option is incorrect because it does not accept user input for the table name. It specifically mentions the "EMP" table instead of using a variable to accept user input.

The correct answer is C. This option is correct because it accepts user input for the columns to be displayed, the table name, and the WHERE condition.

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• Wrong explanation

To determine which users have their SELECT privileges revoked on the SUE.EMP table, we need to analyze the SQL statements provided.

Initially, Sue grants SELECT privileges on sue.EMP to Alice with the GRANT OPTION. This means that Alice can grant these privileges to other users.

Then, Alice grants SELECT privileges on sue.EMP to Rena with the GRANT OPTION. Rena can also grant these privileges to other users.

Finally, Rena grants SELECT privileges on sue.EMP to Timber without the GRANT OPTION.

Afterward, Sue revokes the SELECT privileges on sue.EMP from Alice.

When a user grants privileges with the GRANT OPTION, they can pass on those privileges to other users. However, when a user grants privileges without the GRANT OPTION, they cannot pass on those privileges.

Therefore, the REVOKE command issued by Sue will revoke the SELECT privileges on sue.EMP from Alice. Since Alice granted these privileges to Rena with the GRANT OPTION, Rena will still have the SELECT privileges on sue.EMP. However, since Rena granted these privileges to Timber without the GRANT OPTION, Timber will also lose the SELECT privileges on sue.EMP.

Hence, the correct answer is:

C. Alice, Rena, and Timber

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• Wrong explanation