Management has asked you to calculate the value 12*salary* commission_pct for all the employees in the EMP table. The EMP table contains these columns: LAST NAME VARCNAR2(35) NOT NULL SALARY NUMBER(9,2) NOT NULL COMMISION_PCT NUMBER(4,2) Which statement ensures that a value is displayed in the calculated columns for all employees?

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  1. SELECT last_name, 12*salary* commission_pct FROM emp;

  2. SELECT last_name, 12*salary* (commission_pct,0) FROM emp;

  3. SELECT last_name, 12*salary*(nvl(commission_pct,0)) FROM emp;

  4. SELECT last_name, 12*salary*(decode(commission_pct,0)) FROM emp;

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Correct Option: C
Explanation:

To solve this question, the user needs to know SQL syntax and the concept of NULL values. The user must use the proper SQL function to ensure that all employees' values are displayed in the calculated columns.

Option A: SELECT last_name, 12*salary* commission_pct FROM emp; This option is incorrect because it does not handle NULL values. If any employee has a NULL value in the commission_pct column, the entire expression would result in NULL, and no value would be displayed.

Option B: SELECT last_name, 12*salary* (commission_pct,0) FROM emp; This option is incorrect because it contains a syntax error. The expression (commission_pct, 0) is not valid SQL syntax.

Option C: SELECT last_name, 12*salary*(nvl(commission_pct,0)) FROM emp; This option is correct. The NVL function is used to handle NULL values in the commission_pct column. The function replaces any NULL value with 0, ensuring that all employees have a value in the calculated column.

Option D: SELECT last_name, 12*salary*(decode(commission_pct,0)) FROM emp; This option is incorrect because the DECODE function is not used correctly. The DECODE function should have a second argument to return if the first argument is not equal to 0. Without the second argument, the function would not handle any non-zero values in the commission_pct column.

Therefore, the correct answer is:

The Answer is: C. SELECT last_name, 12*salary*(nvl(commission_pct,0)) FROM emp;

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