举例一个比较好的表连接的执行计划:SQL var loc varchar2(30)SQL exec :loc:=South San FranciscoPL/SQL procedure successfully completed.SQL SELECT 2 emp.last_name,emp.first_name,j.job_title,d.department_name,l.city,l.state_province,l.postal_code,l.street_address, 3 emp.email,e