创建一张表，记录电话呼叫员的工作流水，记录呼叫员编 号、对方号码、通话开始时间、通话结束时间。建表、插数 据等最后都自己写SQL语句。

（1）输出所有数据中通话时间最长的5条记录。orderby

datediff

select top 5*,DATEDIFF(ss,StartDateTime,EndDateTime) as '通话时间(秒)' from CallRecords order by DATEDIFF(ss,StartDateTime,EndDateTime) desc;

---------------------------------------------------------

（2）输出所有数据中拨打长途号码（对方号码以0开头

）的总时长。like、sum

select count(*)as'符合条件',sum(DATEDIFF(ss,StartDateTime,EndDateTime))as '总时长' from CallRecords where TelNum like '0%';

---------------------------------------------------------

（3）输出本月通话总时长最多的前三个呼叫员的编号。

select top 3 CallerNumber as '编号',sum(datediff(ss,StartDateTime,EndDateTime))

from CallRecords

where datepart(mm,StartDateTime)=datepart(mm,getdate())

group by CallerNumber

order by sum(datediff(ss,StartDateTime,EndDateTime)) desc

---------------------------------------------------------

（4）输出本月拨打电话次数最多的前三个呼叫员的编号

.group by,count(*)按照月份分组。

select top 3 CallerNumber,count(*)

from CallRecords

where datepart(mm,StartDateTime)=datepart(mm,getdate())

group by CallerNumber

order by count(*) desc