多项选择题 From SQL*Plus, you issue this SELECT statement: You use this statement to retrieve data from a data table for（）。

单项选择题 EMPLOYEES and DEPARTMENTS data: EMPLOYEES DEMP_NAME DEPT_ID MGR_ID JOB_ID SALARY EMPLOYEE_I 101 Smith 20 120 SA_REP 4000 102 Martin 10 105 CLERK 2500 103 Chris 20 120 IT_ADMIN 4200 104 John 30 108 HR_CLERK 2500 105 Diana 30 108 IT_ADMIN 5000 106 Smith 40 110 AD_ASST 3000 108 Jennifer 30 110 HR_DIR 6500 110 Bob 40 EX_DIR 8000 120 Ravi 20 110 SA_DIR 6500 DEPARTMENTS DEPARTMENT_ID DEPARTMENT_NAME 10 Admin 20 Education 30 IT 40 Human Resources On the EMPLOYEES table, EMPLOYEE_ID is the primary key. MGR_ID is the ID managers and refers to the EMPLOYEE_ID. On the DEPARTMENTS table DEPARTMENT_ID is the primary key. Evaluate this UPDATE statement. UPDATE employees SET mgr_id = (SELECT mgr_id FROM employees WHERE dept_id= (SELECT department_id FROM departments WHERE department_name = Administration)), Salary = (SELECT salary FROM employees WHERE emp_name = Smith) WHERE job_id = IT_ADMIN; What happens when the statement is executed?（）

单项选择题 Evaluate this SQL statement: What will happen if you remove all the parentheses from the calculation?（）