SQL Server一个字符串拆分多行显示或者多行数据合并成一个字符串

概述

• STRING_AGG（合并）：多行数据合并成一个字符串，以逗号隔开。
• STRING_SPLIT（拆分）:一个字符串，拆分成多行。

一、多行数据合并成一个字符串

1、通过 FOR xml path('') 合并字符串记录

根据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 a
group by name;

结果：

2、MS SQL Server的2017新增了STRING_AGG()是一个聚合函数

它将由指定的分隔符分隔将字符串行连接成一个字符串。 它不会在结果字符串的末尾添加分隔符。

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

二、一个字符串拆分成多行

1、拆一列数据：

将如下从Excel复制的一栏数据，插入到表中行进显示（同时去掉回车换行符，空白和Tab符号）：

1、利用XML解析方式(推荐)

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 @table1

insert into @table2  
select   rtrim(ltrim(replace(bs.v1, char(9), "") )),a.xmlval1
from (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) ) bs
where bs.v1 !="";

select * from @table2;

结果：

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 @table2
select rtrim(ltrim(replace(substring(A.col1, B.number, charindex(",", A.col1+",", B.number)-B.number) , char(9), "") )) as col2, B.number
from @table1 A
     inner join master..spt_values B
         on charindex(",", ","+A.col1, B.number)=B.number
where B.type="P";

select * from @table2;

结果：

2、拆多列数据：

有如下数据表

需求就是将Col1，Col2按照特定的字符串分割成多行

先将该字段值统一替换为逗号分割，再将逗号分割替换转为XML数据类型，再利用xml转为多个行

declare @table1 table
    (
        ID int ,
        Col1 nvarchar(50) ,
        Col2 nvarchar(50)
    );

insert into @table1 values ( 1, "a,b,c", "诶，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, v2
from   (   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, v2
from   @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、创建自定义拆分函数

函数功能：切分字符串， 返回一个列名为id的表

--1. 创建fn_Split函数
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 TABLE
AS
    RETURN 
    (
        
        SELECT B.id
        FROM   (
                   (
                          --A　的作用只是生成 "<v>a</v><v>b</v><v>d</v><v>c</v>" 的XML格式的数据, 提供数据源 
                       SELECT [value] = CONVERT(XML, "<v>" + REPLACE(@str, @separator, "</v><v>") + "</v>")
                   ) A 
                   OUTER APPLY
                   (
                          --B 的作用是将A中的 XML 数据的值枚举出来转换成行
                       SELECT id = N.v.value(".", "varchar(100)") FROM   A.[value].nodes("/v") N(v)
                   ) B
               )
    )
GO

使用函数 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 b
where b.id !=""

4、SQL Server 2016新增了string_split函数

专门用来拆分字符串。

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

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