- /*
- sqlServer2005 XML在T-SQL查询中的典型应用
- 整理:fcuandy
- 时间:2008.11.7
- 前言:
- 此文只讲xml数据类型及相应的一些操作方法在解决日常T-sql编程中的一些应用,而避开xml modify,
- xml schema,xml索引,命名空间等这些语法性或者生硬的一些问题(这些语法您可以查联机丛书),即此文主要
- 讲以xml的一些操作特性及xquery去解决编程问题.
- Tags:
- xquery ,FLWOR迭带 ,sql:column ,sql:variable ,nodes ,value ,query ,xpath ,xquery function, if, 聚合函数, xs:function等
- 典型应用举例:
- */
- --(1)
- --====================================================================
- --拆分
- DECLARE @s VARCHAR(100)
- SET @s='a,b,c,dd,ee,f,aa,a,f'
- --常规做法(sql2000常用),以一split函数拆分串为表类型结构,如
- --SELECT * FROM dbo.split(@s,',') a
- --当然,也可能是循环去拆分,或者以一输助表的identity列利用charindex等函数拿identity列值与','的位置匹配实现拆分
- --这些做法,roy_88及本人以前都整理过,不再累赘,可见推荐贴。即便 是xml法,也贴过多次,下面一笔带过
- --XML做法:
- SELECT b.v FROM
- (SELECT CAST('<r>' + REPLACE(@s,'</r><r>') + '</r>' AS XML) x) a --将字串","换换为"</r><r>"并前后拼上<r>,</r>以用来构造xml串
- CROSS APPLY
- (SELECT v=t.x.value('.','VARCHAR(10)') FROM a.x.nodes('//r') AS t(x) ) b --使用 xml.nodes函数将xml串拆分为行
- /*
- a
- b
- c
- dd
- ee
- f
- aa
- a
- aa
- f
- */
- --(2)
- --====================================================================
- --去重,@s中出现的元素,重复的只要一个,希望结果为 'a,f'
- --常规做法,循环或函数,或临时表拆后distinct
- --XML做法:
- --a.在(1)的基础上进行
- ;WITH fc AS --定义cte命名,将@s转换为一个表结构
- (
- SELECT disTINCT b.v v
- FROM
- (SELECT CAST('<r>' + REPLACE(@s,'</r><r>') + '</r>' AS XML) x) a
- CROSS APPLY
- (SELECT v=t.x.value('.','VARCHAR(10)') FROM a.x.nodes('//r') AS t(x) ) b
- )
- --对这个表利用xml方法进行行值拼接
- SELECT STUFF(b.v.value('/r[1]','varchar(100)'),1,'')
- FROM
- (SELECT v=(SELECT ',' + v FROM fc FOR XML PATH(''),ROOT('r'),TYPE)) b
- /*
- a,f
- */
- --b FLWOR语句 + T-sql组合:
- SELECT STUFF(v,'') FROM
- (SELECT CAST('<r>' + REPLACE(@s,'</r><r>') + '</r>' AS XML) x) a
- CROSS APPLY
- (SELECT x=(SELECT t.x.value('.','varchar(10)') v,idx=ROW_NUMBER() OVER(ORDER BY GETDATE()) FROM a.x.nodes('//r') AS t(x) FOR XML PATH('r'),TYPE)) b --利用row_number得到唯一idx
- CROSS APPLY
- (SELECT v=CAST(b.x.query('for $r in //r where count(//r[v=$r/v and idx<$r/idx])=0 return concat(",",xs:string($r/v[1]))') AS VARCHAR(MAX))) c --类似count计数法,取得v相同的节点集idx值最小的节点,原型为:
- --SELECT * FROM tb a WHERE 1>(SELECT COUNT(*) FROM tb WHERE v=a.v AND id<a.id)
- /*
- a ,b ,c ,dd ,ee ,aa ,f
- */
- --c distinct-values
- SELECT REPLACE(v,' ',') FROM
- (SELECT CAST('<r>' + REPLACE(@s,'</r><r>') + '</r>' AS XML) x) a
- CROSS APPLY
- (SELECT CAST(a.x.query('distinct-values(//r)') AS VARCHAR(MAX)) v) b --直接调用distinct-values函数来操作
- /*
- a,aa
- */
- -- 导入去重, last() , position()
- DECLARE @doc xml
- SET @doc ='<?xml version="1.0" encoding="gb2312" ?>
- <employees>
- <employee>
- <empid>e0001</empid>
- <name>萧峰</name>
- </employee>
- <employee>
- <empid>e0002</empid>
- <name>段誉</name>
- </employee>
- <employee>
- <empid>e0003</empid>
- <name>王语嫣</name>
- </employee>
- <employee>
- <empid>e0003</empid>
- <name>张无忌</name>
- </employee>
- </employees>
- '
- create table people2
- (
- personid varchar(10) primary key ,
- name varchar(20)
- )
- INSERT people2
- SELECT disTINCT b.* FROM
- (SELECT x = @doc.query('for $e in //employee return //employee[empid = $e/empid][last()]')) a --FLWOR时,用当前节点去//emploee节点集中找节点集中empid等于当前节点的empid, 在找到的集合中取最后一个利用last()函数
- CROSS APPLY
- (SELECT id=t.x.value('empid[1]',name=t.x.value('name[1]','varchar(100)') FROM a.x.nodes('//employee') AS t(x)) b
- SELECT * FROM people2
- /*
- e0001 萧峰
- e0002 段誉
- e0003 张无忌
- */
- GO
- drop table people2
- GO
- --同组一选多,也可应用此方法,不过没有必要,就不再累赘了。
- --(3)
- --====================================================================
- --列名,列值相关
- --a,按行聚合
- declare @t table(Sname nvarchar(5), V1 float, V2 float, V3 float, V4 float, V5 float, V6 float)
- insert @t select N'张三', 0.11 , 0.21 , 0.29, 0.32 , 0.11, 0.08
- insert @t select N'李四', 0.01 , 0.61 , 0.21, 0.73 , 0.21, 0.12
- insert @t select N'张五', 0.31 , 0.23, 0.33 , 0.91, 0.65
- insert @t select N'张六', 0.59 , 0.11, 0.26, 0.13, 0.01, 0.15
- select b.* from
- (select x=cast((select * from @t for xml path('r')) as xml)) a
- cross apply
- (
- select name=x.query('./Sname/text()'),v=x.query('max(./*[local-name(.)!="Sname"])') from a.x.nodes('//r') as t(x)
- --r为二级节点(因为文档本身无根节点,即为每项的顶级节点)即为一个r节点表示一条记录. r下级节点,每个表示一个列,因为列名未知,所以用/*匹配所有节点,因为name为区别列,不参与聚合运算,故用local-name取得来过滤
- ) b
- /*
- 张三 0.32
- 李四 0.73
- 张五 0.91
- 张六 0.59
- */
- --b ,由值引到取列
- if not object_id('T1') is null
- drop table T1
- GO
- Create table T1([tId] int,[tName] nvarchar(4))
- Insert T1
- select 1,N'zhao' union all
- select 2,N'qian' union all
- select 3,N'sun'
- Go
- --> --> 借且(Roy)生成測試數據
- if not object_id('T2') is null
- drop table T2
- Go
- Create table T2([tId] int,[zhao] nvarchar(1),[qian] nvarchar(1),[sun] nvarchar(1))
- Insert T2
- select 1,N'a',N'b',N'c' union all
- select 2,N'd',N'e',N'f' union all
- select 3,N'g',N'h',N'i'
- Go
- SELECT c.tid,c.tName,v FROM t1 c
- CROSS APPLY
- (SELECT x=(SELECT * FROM t2 WHERE tid=c.tid FOR XML PATH('r'),TYPE)) a
- CROSS APPLY
- (SELECT v=t.x.query('./*[local-name(.)=xs:string(sql:column("c.tName")) ]/text()')
- FROM a.x.nodes('//r') AS t(x)
- ) b
- /*
- 1 zhao a
- 2 qian e
- 3 sun i
- */
- --c, 列名,列值,与系统表
- CREATE TABLE tb(f1 INT,f2 INT,x INT,z INT,d INT,ex INT,dd INT,vv INT)
- INSERT tb SELECT 1,2,3,5,11,2423,33
- GO
- SELECT * FROM tb
- GO
- SELECT name,v FROM
- ( SELECT name FROM sys.columns WHERE object_idobject_id=object_id('tb','u') ) a
- CROSS JOIN
- (SELECT x=(SELECT * FROM tb FOR XML PATH('r'),TYPE)) b
- CROSS APPLY
- (SELECT v=t.x.query('./*[local-name(.)=xs:string(sql:column("a.name")) ]/text()') FROM b.x.nodes('//r') AS t(x) ) c
- /*
- f1 1
- f2 2
- x 3
- z 5
- d 11
- ex 3
- dd 2423
- vv 33
- */
- GO
- DROP TABLE tb
- GO
- --(4)
- --一些综合计算
- --以下表 ta.a值 yyyymmdd-yyyymmdd表连续时间段,","表单个日期
- If object_id('ta','u') is not null
- Drop table ta
- Go
- Create table ta(a varchar(100))
- Go
- Insert into ta
- select '1 ¦ ¦20080101-20080911'
- union all
- select '2 ¦ ¦20080101,20080201,20080301,20080515,20080808'
- union all
- select '3 ¦ ¦20080101,20080201,20080301,20080515,20081108'
- Go
- declare @s varchar(8)
- select @s= convert(varchar(8),getdate(),112)
- select stuff(replace(replace(cast(x as varchar(1000)),'</item><item>',case when type='1' then '-' else ',' end),'</item>',''),6,type + ' ¦ ¦') a
- from
- (
- select left(a,1) type,
- cast(
- '<item>'
- +
- replace(
- stuff(a,
- case when left(a,1)=1 then '-' else ',' end,
- '</item><item>'
- )
- +
- '</item>'
- AS XML
- ) x
- from ta
- ) base
- where x.value('
- if (sql:column("base.type")="1") then
- if(
- (/item/text())[1]<sql:variable("@s")
- and
- (/item/text())[2]>sql:variable("@s")
- )
- then 1
- else 0
- else
- count(//item[text()>sql:variable("@s")])
- '
- ,
- 'int'
- )>0
- go