【统计】找出就职年份最高的雇员(列出雇员名字+年份）【分组】按角色(Role)统计一下每个角色的平均就职年份【分组】按办公室名字总计一下就职年份总和【难题】每栋办公室按人数排名,不要统计无办公室的雇员统计】找出就职年份最高的雇员(列出雇员名字+年份）【答案】SELECT Name,Max(Years_employed) FROM employees【分组】按角色(Role)统计一下每个角色的平均就职年份【答案】SELECT Role,avg(Years_employed) FROM employees group by Role【分组】按办公室名字总计一下就职年份总和【答案】SELECT building,sum(Years_employed) FROM employees group by Building【难题】每栋办公室按人数排名,不要统计无办公室的雇员【答案】SELECT building,count(*) as count FROM employees where building is NOT null group by building Role Name Building Years_employed Engineer Becky A. 1e 4 Engineer Dan B. 1e 2 Engineer Sharon F. 1e 6 Engineer Dan M. 1e 4 Engineer Malcom S. 1e 1 Artist Tylar S. 2w 2 Artist Sherman D. 2w 8 Artist Jakob J. 2w 6 Artist Lillia A. 2w 7 Artist Brandon J. 2w 7 Manager Scott K. 1e 9 Manager Shirlee M. 1e 3 Manager Daria O. 2w 6 Engineer Yancy I. null 0 Artist Oliver P. null 0