SQL uses the for XML path to implement string concatenation

In SQL, it is often necessary to synthesize multiple rows of data into one line below is a brief introduction to using the for XML path.

1, convert the Tuyi to figure two:

 1  select   ArticleID,  2  (select  convert  (varchar  (10 ), TagID) +   "   " from   3  for  XML PATH ( Span style= "color: #ff0000;" '  ') as  tagID from  ARTICLETAG_TB group  by  ArticleID 

The above is a table, the following look at the practice of multi-table association, is actually the same as just the connection table query
This is an example of an article that corresponds to more than one label three sheets:

CREATE TABLE [dbo].[ARTICLE_TB](    [ArticleID] [int] NULL,    [ArticleName] [nvarchar]( -)NULL)CREATE TABLE [dbo].[ARTICLETAG_TB](    [ArticleID] [int] NULL,    [TagID] [int] NULL)CREATE TABLE [dbo].[TAG_TB](    [TagID] [int] NULL,    [TagName] [nvarchar]( -)NULL)

Implement the SQL statement:

SELECTArticleName, (SELECTTagName+',' from(SELECTA.articlename,t.tagname fromARTICLE_TB A Left JOINARTICLETAG_TB at onAt.articleid=A.articleid Left JOINTAG_TB T onAt.tagid=T.tagid)TempWHERE Temp. articlename=Tt.articlename forXML PATH ("')) asTagName fromARTICLE_TB TT

Explain:
Connect three tables first to find the required fields, and then use the for XML PATH self-Join stitching string

The result of a three-table connection query is: Using the for XML path stitching result:

SQL uses the for XML path to implement string concatenation