数据库>SQL Server2005>第4季SQL从入门到提高>13练习1

表结构如下：

相关查询：

--所有数据中通话时间最长的5条记录
select top 5 * from CallRecords1
order by dateDiff(second,StartDateTime,EndDateTime) desc

--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 sum(dateDiff(second,StartDateTime,EndDateTime)) from CallRecords1
where TelNum like '0%'

--输出本月拨打电话次数最多的前三个呼叫员的编号
select * from CallRecords1

--分组出，每个呼叫员打的电话次数
select CallerNumber,count(*) from CallRecords1
group by CallerNumber

--根据每个呼叫员打的电话次数进行排序，然后取前三
select top 3 CallerNumber,count(*) as countsNumber from CallRecords1
 group by CallerNumber order by countsNumber desc

--汇总（市内号码总时长）（长途号码总时长）
select * from CallRecords1

--市内号码，TelNum开头不带0，的每个拨打时长秒数
select datediff(second,StartDateTime,EndDateTime) from CallRecords1
where TelNum not like '0%'

--进行汇总
select sum(datediff(second,StartDateTime,EndDateTime)) as 市内号码
from CallRecords1
where TelNum not like '0%'

--对长途号码，也如下统计
select sum(datediff(second,StartDateTime,EndDateTime)) as 长途
from CallRecords1
where TelNum like '0%'

--两者结合在一起
select (
select sum(datediff(second,StartDateTime,EndDateTime)) as 市内号码
from CallRecords1
where TelNum not like '0%'
) as 市内号码,
(
select sum(datediff(second,StartDateTime,EndDateTime)) as 长途
from CallRecords1
where TelNum like '0%'
)as 长途号码

--第二种方法汇总
select sum((
case
when TelNum not like '0%' then datediff(second,StartDateTime,EndDateTime)
else 0
end
))as 市内号码,
sum((
case
when TelNum like '0%' then datediff(second,StartDateTime,EndDateTime)
else 0
end
))as 长途号码
from CallRecords1

 

--呼叫员编号，对方号码，通话时长，加汇总
select CallerNumber,TelNum,datediff(second,StartDateTime,EndDateTime) from CallRecords1
union all
select N'汇总',(
select convert(varchar(50),sum(datediff(second,StartDateTime,EndDateTime)))
from CallRecords1
where TelNum not like '0%'
),
(
select sum(datediff(second,StartDateTime,EndDateTime))
from CallRecords1
where TelNum like '0%'
)

--如果没进行convert转换，你看下查询结果，思考有啥不同