What does the following SQL script do? SELECT AVG(MAX(salary)) FROM employees GROUP BY department_id;

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  1. it has a syntax error, the AVG clause is not valid

  2. it calculates the average of the maximum salaries of all the departments

  3. it has a syntax error, the MAX clause is not valid

  4. it has no error, but the GROUP BY clause is not effective

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Correct Option: B

AI Explanation

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

Option A) It has a syntax error, the AVG clause is not valid - This option is incorrect because the AVG clause is valid in SQL and is used to calculate the average value of a column.

Option B) It calculates the average of the maximum salaries of all the departments - This option is correct. The SQL script calculates the maximum salary for each department using the MAX function and then calculates the average of these maximum salaries using the AVG function. The result will be the average of the maximum salaries for all departments.

Option C) It has a syntax error, the MAX clause is not valid - This option is incorrect because the MAX clause is valid in SQL and is used to find the maximum value of a column.

Option D) It has no error, but the GROUP BY clause is not effective - This option is incorrect. The GROUP BY clause is effective in this script because it groups the records by the department_id column, allowing the script to calculate the maximum salary for each department separately.

The correct answer is B. This option is correct because the script calculates the average of the maximum salaries of all the departments.

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