SQL Server to combine multi rows into single row where col0=col1 - sql-server

Question

my table :
previousid|CurrentID|Data
| 1 | 2 | Data 1
| 2 | 3 | Data 2
| 3 | 4 | Data 3
| 4 | 5 | Data 4
Result i look for :
Select .... where PreviousID=1 :
|Col0|Col1|Col2 |Col3|Col 4|Col5| Col6 | Col7 | Col8
|1 |2 |Data 1|3 |Data 2| 4 | data 3| 5 | data 4
Select .....where PreviousID=2
|Col0|Col1|Col2 |Col3|Col 4|Col5| Col6 |
|2 |3 |Data 2|4 |Data 3| 5 | data 4|
i tried to create some SQL server query to get result with no luck, please help me guys

Answer 1

We can do this in a few steps:
Declare and set a variable to use for our root node, and create a temporary table to store the results from our recusive query:
Insert the results from the recusive query into the temporary table
Generate and execute dynamic sql to pivot() the temporary table.
(alternate) Generate and execute dynamic sql to use conditional aggregation instead of pivot():
rextester demo: http://rextester.com/MRFZC75180
test setup:
create table t (PreviousID int, CurrentID int, Data varchar(32));
insert into t values
(1,2,'Data 1'),(2,3,'Data 2'),(3,4,'Data 3'),(4,5,'Data 4');
Declare and set a variable to use for our root node, and create a temporary table to store the results from our recusive query:
declare #PreviousId int = 2;
create table #temp (PreviousID int
, Level int
, Col varchar(32)
, Value varchar(32)
, rn int
);
Insert the results from the recusive query into the temporary table
;with cte as (
select PreviousID, CurrentID, Data, level = 0
from t
where previousId = #PreviousId
union all
select c.PreviousID, c.CurrentID, c.Data, level = p.level +1
from t c
inner join cte as p
on c.PreviousID = p.CurrentID
)
insert into #temp
select p.PreviousId, t.level, x.col, x.value
, rn = row_number() over (order by t.level, x.col)
from cte t
cross apply (
select top 1
PreviousId
from cte i
order by level
) as p (PreviousId)
cross apply (
values ('CurrentId',convert(varchar(32),CurrentId)),('Data',Data)
) as x (col,value);
results so far:
+------------+-------+-----------+--------+----+
| PreviousID | Level | Col | Value | rn |
+------------+-------+-----------+--------+----+
| 2 | 0 | CurrentId | 3 | 1 |
| 2 | 0 | Data | Data 2 | 2 |
| 2 | 1 | CurrentId | 4 | 3 |
| 2 | 1 | Data | Data 3 | 4 |
| 2 | 2 | CurrentId | 5 | 5 |
| 2 | 2 | Data | Data 4 | 6 |
+------------+-------+-----------+--------+----+
Generate and execute dynamic sql to pivot() the temporary table.
/* pivot */
declare #cols nvarchar(max);
declare #sql nvarchar(max);
select #cols = stuff((
select
', Col'+convert(nvarchar(10),rn)
from #temp
order by 1
for xml path (''), type).value('.','nvarchar(max)')
,1,1,'')
select #sql ='
select Col0=PreviousID, ' + #cols +'
from (
select PreviousID, Value, rn= ''Col''+convert(nvarchar(10),rn)
from #temp
) as t
pivot (max([Value]) for [rn] in (' + #cols +')) p'
select #sql as CodeGenerated;
exec sp_executesql #sql;
code generated:
select Col0=PreviousID, Col1, Col2, Col3, Col4, Col5, Col6
from (
select PreviousID, Value, rn= 'Col'+convert(nvarchar(10),rn)
from #temp
) as t
pivot (max([Value]) for [rn] in ( Col1, Col2, Col3, Col4, Col5, Col6)) p
returns:
+------+------+--------+------+--------+------+--------+
| Col0 | Col1 | Col2 | Col3 | Col4 | Col5 | Col6 |
+------+------+--------+------+--------+------+--------+
| 2 | 3 | Data 2 | 4 | Data 3 | 5 | Data 4 |
+------+------+--------+------+--------+------+--------+
(alternate) Generate and execute dynamic sql to use conditional aggregation instead of pivot():
/* conditional aggregation */
--declare #cols nvarchar(max);
--declare #sql nvarchar(max);
select #cols = stuff((
select
char(10)+' , '
+ 'Col'+convert(nvarchar(10),rn)
+' = max(case when rn = '+convert(nvarchar(10),rn)+' then Value end)'
from #temp
order by 1
for xml path (''), type).value('.','nvarchar(max)')
,1,0,'')
select #sql ='
select Col0 = PreviousID'+#cols+'
from #temp
group by PreviousID'
select #sql as CodeGenerated;
exec sp_executesql #sql;
code generated:
select Col0 = PreviousID
, Col1 = max(case when rn = 1 then Value end)
, Col2 = max(case when rn = 2 then Value end)
, Col3 = max(case when rn = 3 then Value end)
, Col4 = max(case when rn = 4 then Value end)
, Col5 = max(case when rn = 5 then Value end)
, Col6 = max(case when rn = 6 then Value end)
from #temp
group by PreviousID
returns:
+------+------+--------+------+--------+------+--------+
| Col0 | Col1 | Col2 | Col3 | Col4 | Col5 | Col6 |
+------+------+--------+------+--------+------+--------+
| 2 | 3 | Data 2 | 4 | Data 3 | 5 | Data 4 |
+------+------+--------+------+--------+------+--------+

Answer 2

I think try with concatenating column and give them alias.
For better understanding go through this link https://www.mssqltips.com/sqlservertip/2985/concatenate-sql-server-columns-into-a-string-with-concat/