执行Command的ExecuteScalar方法得到的是结果集中的第2行第2列。
热油系统供用户按温度不同分为二种,其温度为() 310℃,165℃。 320℃,176℃。 315.6℃,176.7℃。
Examine the structure of the EMPLOYEES and DEPARTMENTS tables: EMPLOYEES EMPLOYEE_ID NUMBER DEPARTMENT_ID NUMBER MANAGER_ID NUMBER LAST_NAME VARCHAR2(25) DEPARTMENTS DEPARTMENT_ID NUMBER MANAGER_ID NUMBER DEPARTMENT_NAME VARCHAR2(35) LOCATION_ID NUMBER You want to create a report displaying employee last names, department names, and locations. Which query should you use?() SELECT e.last_name, d. department_name, d.location_id FROM employees e NATURAL JOIN departments D USING department_id ;。 SELECT last_name, department_name, location_id FROM employees NATURAL JOIN departments WHERE e.department_id =d.department_id;。 SELECT e.last_name, d.department_name, d.location_id FROM employees e NATURAL JOIN departments d;。 SELECT e.last_name, d.department_name, d.location_id FROM employees e JOIN departments d USING (department_id )。
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MustInherit修饰符用于"抽象类"。
用直流电桥测量开关的接触电阻时,电桥指示的电阻随时间的增大而()。