单项选择题 Which of the following SQL statements will return the year and average salary for all employees hired within a given year that have a salary greater than $30,000?（）

单项选择题 Given the following table definition: STOCK: item VARCHAR(30) status CHAR(1) quantity INT price DEC(7,2) If items are indicated to be out of stock by setting STATUS to NULL and QUANTITY and PRICE to zero, which of the following statements would be used to update the STOCK table to indicate that all the items whose description begins with the letter "S" are out of stock?（）

单项选择题 The EMPLOYEE table contains the following information: EMPNO NAME WORKDEPT 101 SAM A11 102 JOHN C12 103 JANE -104 PAT Remote 105 ANNE -106 BOB A11 The MANAGER table contains the following information: MGRID NAME DEPTNO EMPCOUNT 1 WU B01 - 2 JONES A11 - 3 CHEN - - 4 SMITH - -5 THOMAS C12 - After this statement is executed: UPDATE manager m SET empcount = (SELECT COUNT(workdept) FROM employee e WHERE workdept=m.deptno) What is the result of the following query?（） SELECT mgrid, empcount FROM MANAGER WHERE empcount IS NOT NULL ORDER BY mgrid