TSQL Table Transformation Fields => Columns - sql

Question

I have the following table layout. Each line value will always be unique. There will never be more than one instance of the same Id, Name, and Line.
Id Name Line
1 A Z
2 B Y
3 C X
3 C W
4 D W
I would like to query the data so that the Line field becomes a column. If the value exists, a 1 is applied in the field data, otherwise a 0. e.g.
Id Name Z Y X W
1 A 1 0 0 0
2 B 0 1 0 0
3 C 0 0 1 1
4 D 0 0 0 1
The field names W, X, Y, Z are just examples of field values, so I can't apply an operator to explicitly check, for example, 'X', 'Y', or 'Z'. These could change at any time and are not restricted to a finate set of values. The column names in the result-set should reflect the unique field values as columns.
Any idea how I can accomplish this?

Answer 1

It's a standard pivot query.
If 1 represents a boolean indicator - use:
SELECT t.id,
t.name,
MAX(CASE WHEN t.line = 'Z' THEN 1 ELSE 0 END) AS Z,
MAX(CASE WHEN t.line = 'Y' THEN 1 ELSE 0 END) AS Y,
MAX(CASE WHEN t.line = 'X' THEN 1 ELSE 0 END) AS X,
MAX(CASE WHEN t.line = 'W' THEN 1 ELSE 0 END) AS W
FROM TABLE t
GROUP BY t.id, t.name
If 1 represents the number of records with that value for the group, use:
SELECT t.id,
t.name,
SUM(CASE WHEN t.line = 'Z' THEN 1 ELSE 0 END) AS Z,
SUM(CASE WHEN t.line = 'Y' THEN 1 ELSE 0 END) AS Y,
SUM(CASE WHEN t.line = 'X' THEN 1 ELSE 0 END) AS X,
SUM(CASE WHEN t.line = 'W' THEN 1 ELSE 0 END) AS W
FROM TABLE t
GROUP BY t.id, t.name

Answer 2

Edited following update in question
SQL Server does not support dynamic pivoting.
To do this you could either use dynamic SQL to generate a query along the following lines.
SELECT
Id ,Name,
ISNULL(MAX(CASE WHEN Line='Z' THEN 1 END),0) AS Z,
ISNULL(MAX(CASE WHEN Line='Y' THEN 1 END),0) AS Y,
ISNULL(MAX(CASE WHEN Line='X' THEN 1 END),0) AS X,
ISNULL(MAX(CASE WHEN Line='W' THEN 1 END),0) AS W
FROM T
GROUP BY Id ,Name
Or an alternative which I have read about but not actually tried is to leverage the Access Transform function by setting up an Access database with a linked table pointing at the SQL Server table then query the Access database from SQL Server!

Answer 3

Here is the dynamic version
Test table
create table #test(id int,name char(1),line char(1))
insert #test values(1 , 'A','Z')
insert #test values(2 , 'B','Y')
insert #test values(3 , 'C','X')
insert #test values(4 , 'C','W')
insert #test values(5 , 'D','W')
insert #test values(5 , 'D','W')
insert #test values(5 , 'D','P')
Now run this
declare #names nvarchar(4000)
SELECT #names =''
SELECT #names = #names + line +', '
FROM (SELECT distinct line from #test) x
SELECT #names = LEFT(#names,(LEN(#names) -1))
exec('
SELECT *
FROM(
SELECT DISTINCT Id, Name,Line
FROM #test
) AS pivTemp
PIVOT
( COUNT(Line)
FOR Line IN (' + #names +' )
) AS pivTable ')
Now add one row to the table and run the query above again and you will see the B
insert #test values(5 , 'D','B')
Caution: Of course all the problems with dynamic SQL apply, if you can use sp_executeSQL but since parameters are not use like that in the query there really is no point

Answer 4

Assuming you have a finite number of values for Line that you could enumerate:
declare #MyTable table (
Id int,
Name char(1),
Line char(1)
)
insert into #MyTable
(Id, Name, Line)
select 1,'A','Z'
union all
select 2,'B','Y'
union all
select 3,'C','X'
union all
select 3,'C','W'
union all
select 4,'D','W'
SELECT Id, Name, Z, Y, X, W
FROM (SELECT Id, Name, Line
FROM #MyTable) up
PIVOT (count(Line) FOR Line IN (Z, Y, X, W)) AS pvt
ORDER BY Id

Answer 5

As you are using SQL Server, you could possibly use the PIVOT operator intended for this purpose.

Answer 6

If you're doing this for a SQL Server Reporting Services (SSRS) report, or could possibly switch to using one, then stop now and go throw a Matrix control onto your report. Poof! You're done! Happy as a clam with your data pivoted.

Answer 7

Here's a rather exotic approach (using sample data from the old Northwind database). It's adapted from the version here, which no longer worked due to the deprecation of DBCC RENAMECOLUMN and the addition of PIVOT as a keyword.
set nocount on
create table Sales (
AccountCode char(5),
Category varchar(10),
Amount decimal(8,2)
)
--Populate table with sample data
insert into Sales
select customerID, 'Emp'+CAST(EmployeeID as char), sum(Freight)
from Northwind.dbo.orders
group by customerID, EmployeeID
create unique clustered index Sales_AC_C
on Sales(AccountCode,Category)
--Create table to hold data column names and positions
select A.Category,
count(distinct B.Category) AS Position
into #columns
from Sales A join Sales B
on A.Category >= B.Category
group by A.Category
create unique clustered index #columns_P on #columns(Position)
create unique index #columns_C on #columns(Category)
--Generate first column of Pivot table
select distinct AccountCode into Pivoted from Sales
--Find number of data columns to be added to Pivoted table
declare #datacols int
select #datacols = max(Position) from #columns
--Add data columns one by one in the correct order
declare #i int
set #i = 0
while #i < #datacols begin
set #i = #i + 1
--Add next data column to Pivoted table
select P.*, isnull((
select Amount
from Sales S join #columns C
on C.Position = #i
and C.Category = S.Category
where P.AccountCode = S.AccountCode),0) AS X
into PivotedAugmented
from Pivoted P
--Name new data column correctly
declare #c sysname
select #c = Category
from #columns
where Position = #i
exec sp_rename '[dbo].[PivotedAugmented].[X]', #c, 'COLUMN'
--Replace Pivoted table with new table
drop table Pivoted
select * into Pivoted from PivotedAugmented
drop table PivotedAugmented
end
select * from Pivoted
go
drop table Pivoted
drop table #columns
drop table Sales