How to get previous row value in present row in sql server-CodePudding

Is there a way we can get previous row data in present row in SQL Server

For eg I have a table as

id  |  name
1   |  abc
2   |  def
3   |  xyz

I need to query data in the following manner .. so as to concatenate previous row with present one

This way

id  |  name
1   |  abc
2   |  abcdef
3   |  abcdefxyz

I tries with lag() but, couldn't figure out what am I doing wrong. I am very new in SQL Server.. I am not aware of other functions that could help

Thanks in advance

CodePudding user response：

you can use String_agg function like below

create table t (id  int,  name nvarchar(max));
insert into t values (1 , 'abc'),(2, 'def'),(3,'xyz');

select t1.id,string_agg(t2.name,'') from t t1 left join t t2 
on t1.id>=t2.id
group by t1.id

demo link