概述

• STRING_AGG（合并）：多行數據合并成一個字符串，以逗號隔開。
• STRING_SPLIT（拆分）:一個字符串，拆分成多行。

一、多行數據合并成一個字符串

1、通過 FOR xml path('') 合并字符串記錄

根據name字段，合并code

declare  @table1  table (    id int ,code varchar(10) , name varchar(20) ); insert into @table1 ( id,code, name ) values ( 1, "m1","a" ), ( 2,  "m2",null ), ( 3, "m3", "c" ), ( 4,  "m2","d" ), ( 5,  "m1","c" );select * from @table1;select name, files=stuff((select ","+convert(varchar, code)  from @table1 b  where a.name=b.name for xml path("")), 1, 1, "")from @table1 agroup by name;

結果：

2、MS SQL Server的2017新增了STRING_AGG()是一個聚合函數

它將由指定的分隔符分隔將字符串行連接成一個字符串。 它不會在結果字符串的末尾添加分隔符。

SELECT  name,   string_agg(code,";") files FROM @table1 GROUP BY name;

二、一個字符串拆分成多行

1、拆一列數據：

將如下從Excel復制的一欄數據，插入到表中行進顯示（同時去掉回車換行符，空白和Tab符號）：

1、利用XML解析方式(推薦)

declare @moulds varchar(4000);set @moulds="55-480730-03,55-487780-01,, 55-487780-02 ";declare @table1 table(col1 nvarchar(4000));declare @table2 table(col1 nvarchar(40),xmlval1 xml);insert into @table1 values(replace(@moulds, char(13)+char(10), ""));select * from @table1insert into @table2  select   rtrim(ltrim(replace(bs.v1, char(9), "") )),a.xmlval1from (select convert(xml, "<n>"+replace(replace(col1, "，", ","), ",", "</n><n>")+"</n>") as xmlval1         from @table1) a       cross apply(select k.n.value(".", "nvarchar(80)") v1 from a.xmlval1.nodes("n") k(n) ) bswhere bs.v1 !="";select * from @table2;

結果：

2、利用字符串拆解

declare @moulds varchar(4000);set @moulds="55-480730-03,55-487780-01,, 55-487780-02 ";declare @table1 table(col1 nvarchar(4000));declare @table2 table(col1 nvarchar(40), pos int);insert into @table1 values(replace(@moulds, char(13)+char(10), ""));select * from @table1;insert into @table2select rtrim(ltrim(replace(substring(A.col1, B.number, charindex(",", A.col1+",", B.number)-B.number) , char(9), "") )) as col2, B.numberfrom @table1 A     inner join master..spt_values B on charindex(",", ","+A.col1, B.number)=B.numberwhere B.type="P";select * from @table2;

結果：

2、拆多列數據：

有如下數據表

需求就是將Col1，Col2按照特定的字符串分割成多行

先將該字段值統一替換為逗號分割，再將逗號分割替換轉為XML數據類型，再利用xml轉為多個行

declare @table1 table    (ID int ,Col1 nvarchar(50) ,Col2 nvarchar(50)    );insert into @table1 values ( 1, "a,b,c", "誒，必，塞，地，伊" );insert into @table1 values ( 2, "w", N"三四，不知道咧" );--方式一select a.ID, a.Col1, a.Col2,  v1, v2from   (   select ID, Col1, Col2, convert(xml, "<n>" + replace(replace(Col1, "，", ","), ",", "</n><n>") + "</n>") as xmlval1 ,  convert(xml, "<n>" + replace(replace(Col2, "，", ","), ",", "</n><n>") + "</n>") as xmlval2   from   @table1 ) a       cross apply (   select k.n.value(".", "nvarchar(80)") v1       from   a.xmlval1.nodes("n") k(n) ) bs       cross apply (   select k.n.value(".", "nvarchar(80)") v2       from   a.xmlval2.nodes("n") k(n) ) ns;--方式二select ID, t.Col1,t.Col2,  v1, v2from   @table1 as t       cross apply ( values (convert(xml, "<n>" + replace(replace(Col1, "，", ","), ",", "</n><n>")+ "</n>"),      convert(xml, "<n>" + replace(replace(Col2, "，", ","), ",", "</n><n>")+ "</n>"))   ) a (xmlval1 , xmlval2 )       cross apply (   select k.n.value(".", "varchar(80)") as v1       from   a.xmlval1.nodes("n") k(n)) bs       cross apply (   select k.n.value(".", "varchar(80)") as v2       from   a.xmlval2.nodes("n") k(n) ) ns;

3、創建自定義拆分函數

函數功能：切分字符串， 返回一個列名為id的表

--1. 創建fn_Split函數IF EXISTS(       SELECT *       FROM   dbo.sysobjects       WHERE  id = OBJECT_ID("fn_Split")      AND (TYPE = "FN" OR TYPE = "TF" OR TYPE = "IF")   )    DROP FUNCTION fn_Split  GO     CREATE FUNCTION [dbo].[fn_Split](    @str   VARCHAR(MAX),    @separator     VARCHAR(10))RETURNS TABLEAS    RETURN     (SELECT B.idFROM   (   (  --A　的作用只是生成 "<v>a</v><v>b</v><v>d</v><v>c</v>" 的XML格式的數據, 提供數據源        SELECT [value] = CONVERT(XML, "<v>" + REPLACE(@str, @separator, "</v><v>") + "</v>")   ) A    OUTER APPLY   (  --B 的作用是將A中的 XML 數據的值枚舉出來轉換成行       SELECT id = N.v.value(".", "varchar(100)") FROM   A.[value].nodes("/v") N(v)   ) B       )    )GO

使用函數 SELECT id FROM fn_Split('a,b,d,c',',')

declare @moulds varchar(4000);set @moulds="55-480730-03,55-487780-01,, 55-487780-02 ";declare @table1 table(id INT,col1 nvarchar(MAX));INSERT INTO @table1 VALUES(1,replace(@moulds, char(13)+char(10), ""))INSERT INTO @table1 VALUES(2,replace(@moulds, char(13)+char(10), ""))select * from @table1;SELECT a.id,rtrim(ltrim(replace(b.id, char(10), "") )) AS item FROM @table1 a CROSS APPLY dbo.fn_Split(a.col1,",") AS bwhere b.id !=""

4、SQL Server 2016新增了string_split函數

專門用來拆分字符串。

SELECT t.id,       t.name,       t.description,       v.valueFROM test t    CROSS APPLY STRING_SPLIT(t.description, ",")v;

到此這篇關于SQL Server一個字符串拆分多行顯示或者多行數據合并成一個字符串的文章就介紹到這了。希望對大家的學習有所幫助，也希望大家多多支持。