题目是这样的
查询热门图书(被借次数在前5位)的图书编号、图书名称、被借次数,
以及借过此书的学生姓名(读者列表)。要求多个学生中间用“、”隔开,若某
学生多次借阅此书,不要重复显示,读者列表中学生的排列顺序按照借阅此书
次数从大到小排序,此书次数一样多的按照姓名的拼音从小到大排序。(以网格的形式显示)有三张表,book(bookID,title,author),borrow(borrowID,stuID,bookID,borrowTime,returnTime),
stuent(stuID,stuName,major).
请高手赐教。老师说用游标。
查询热门图书(被借次数在前5位)的图书编号、图书名称、被借次数,
以及借过此书的学生姓名(读者列表)。要求多个学生中间用“、”隔开,若某
学生多次借阅此书,不要重复显示,读者列表中学生的排列顺序按照借阅此书
次数从大到小排序,此书次数一样多的按照姓名的拼音从小到大排序。(以网格的形式显示)有三张表,book(bookID,title,author),borrow(borrowID,stuID,bookID,borrowTime,returnTime),
stuent(stuID,stuName,major).
请高手赐教。老师说用游标。
borrowcnt = count(1) stuff((select distinct '、' + b.stuname from borrow a join student b on a.stuid = b.stuid where a.bookid = c.bookid for xml path('')),1,1,'')
from borrow c join book d on c.bookid = d.bookdi
group by c.bookid, d.title
order by count(1), d.title请记得结贴哦用游标的写法,请楼下的补充。
studentlist = stuff((select distinct '、' + b.stuname from borrow a join student b on a.stuid = b.stuid where a.bookid = c.bookid for xml path('')),1,1,'')
from borrow c join book d on c.bookid = d.bookdi
group by c.bookid, d.title
order by count(1), d.title
先用
select top 5 bookID
from borrow
group by bookID
order by count(1) desc
取出最大五条用游票的话
declare cur cursor for
select bookID from #tmp
open cur
fetch next from cur into @bookID
while @@fetch_status = 0
begin
...处理语句 fetch next from cur into @bookIDend
close cur
deallocate cur
标题:按某字段合并字符串之一(简单合并)
作者:爱新觉罗.毓华(十八年风雨,守得冰山雪莲花开)
时间:2008-11-06
地点:广东深圳描述:将如下形式的数据按id字段合并value字段。
id value
----- ------
1 aa
1 bb
2 aaa
2 bbb
2 ccc
需要得到结果:
id value
------ -----------
1 aa,bb
2 aaa,bbb,ccc
即:group by id, 求 value 的和(字符串相加)
*/
--1、sql2000中只能用自定义的函数解决
create table tb(id int, value varchar(10))
insert into tb values(1, 'aa')
insert into tb values(1, 'bb')
insert into tb values(2, 'aaa')
insert into tb values(2, 'bbb')
insert into tb values(2, 'ccc')
gocreate function dbo.f_str(@id varchar(10)) returns varchar(1000)
as
begin
declare @str varchar(1000)
select @str = isnull(@str + ',' , '') + cast(value as varchar) from tb where id = @id
return @str
end
go--调用函数
select id , value = dbo.f_str(id) from tb group by iddrop function dbo.f_str
drop table tb
--2、sql2005中的方法
create table tb(id int, value varchar(10))
insert into tb values(1, 'aa')
insert into tb values(1, 'bb')
insert into tb values(2, 'aaa')
insert into tb values(2, 'bbb')
insert into tb values(2, 'ccc')
goselect id, [value] = stuff((select ',' + [value] from tb t where id = tb.id for xml path('')) , 1 , 1 , '')
from tb
group by iddrop table tb
--3、使用游标合并数据
create table tb(id int, value varchar(10))
insert into tb values(1, 'aa')
insert into tb values(1, 'bb')
insert into tb values(2, 'aaa')
insert into tb values(2, 'bbb')
insert into tb values(2, 'ccc')
go
declare @t table(id int,value varchar(100))--定义结果集表变量
--定义游标并进行合并处理
declare my_cursor cursor local for
select id , value from tb
declare @id_old int , @id int , @value varchar(10) , @s varchar(100)
open my_cursor
fetch my_cursor into @id , @value
select @id_old = @id , @s=''
while @@FETCH_STATUS = 0
begin
if @id = @id_old
select @s = @s + ',' + cast(@value as varchar)
else
begin
insert @t values(@id_old , stuff(@s,1,1,''))
select @s = ',' + cast(@value as varchar) , @id_old = @id
end
fetch my_cursor into @id , @value
END
insert @t values(@id_old , stuff(@s,1,1,''))
close my_cursor
deallocate my_cursorselect * from @t
drop table tb