----对字符串进行排序
---对字符串DCCBBABA 执行之后变成 AABBBCCD
declare @str nvarchar(20)
set @str='DCCBBABA'
 select replicate('A',(len(@str)-len(replace(@str,'A',''))))+
replicate('B',(len(@str)-len(replace(@str,'B','')))) +
replicate('C',(len(@str)-len(replace(@str,'C','')))) +
replicate('D',(len(@str)-len(replace(@str,'D',''))))

---电影院座位预订(未成功)
---电影院预定连号的座位号约束
--预订规则是两片连号的座位不能重叠
create table filmeSeat
(
reserver nvarchar(20) not null primary key
,startSeat int not null,
finishSeat int not null
)
go
insert filmeSeat
select '张三',1,4 union
select '李四',6,7 union
select '王五',21,24 union
select '赵六',11,14 union
select '钱七',16,18

go
drop table filmeSeat
--go
--create table filmeSeat
--(
--reserver nvarchar(20) not null primary key
--,startSeat int not null,
--finishSeat int not null,
--check(startSeat<=finishSeat))
--go
------在Check中不允许使用子查询。只允许使用标量表达式。
--ALTER TABLE filmeSeat
--ADD CONSTRAINT no_overlaps
--check(not exists (select t1.reserver from filmeSeat as t1
--where filmeSeat.startSeat between t1.startSeat and t1.finishSeat
--or filmeSeat.finishSeat between t1.startSeat and t1.finishSeat)
--)

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出处：https://www.cnblogs.com/chillsrc/archive/2011/11/22/2259589.html