EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO 7369 SMITH CLERK 7902 17-DEC-80 800 NULL 20 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7565 EMILY SALESMAN 7698 20-FEB-81 1250 800 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7655 JONES MANAGER 7839 2-APR-81 2975 NULL 20 7698 BLAKE MANAGER 7839 1-MAY-91 2850 NULL 30 7782 CLARK MANAGER 7839 9-JUN-81 2450 NULL 10 7788 SCOTT ANALYST 7655 21-MAR-87 3000 NULL 20 7844 TURNER SALESMAN 7698 18-SEP-81 1500 NULL 30 7876 ADAMS CLERK 7788 24-APR-87 1100 NULL 20 7900 JAMES CLERK 7698 3-DEC-81 950 NULL 30 7902 FORD ANALYST 7655 3-DEC-81 3000 NULL 20 7934 MILLER CLERK 7782 3-JAN-81 1300 NULL 10 Given This Table Called 'EMP', please define a function that, given a department number, returns the average salary of that department.

Sure, here's the function in SQL:

CREATE FUNCTION avg_salary_dept (dept_no INT) RETURNS DECIMAL(10, 2)
BEGIN
    DECLARE total_salary DECIMAL(10, 2);
    DECLARE num_employees INT;
    SELECT SUM(sal) INTO total_salary, COUNT(*) INTO num_employees FROM EMP WHERE DEPTNO = dept_no;
    RETURN total_salary / num_employees;
END;

This function takes in a department number and returns the average salary of employees in that department. It uses the SQL `SUM` function to add up all the salaries of employees in the department, and the `COUNT` function to get the number of employees in the department. Then it calculates the average salary by dividing the total salary by the number of employees, and returns the result.