Transposing a SQL query result - sql

Question

I have a query that produces a table that looks like this:
+----------------+-----------+------------+----------+
| CustomerNumber | FirstName | MiddleName | LastName |
+----------------+-----------+------------+----------+
| 123456 | Test | Test1 | Test2 |
+----------------+-----------+------------+----------+
What I am needing is for the table to look like this:
+----------------+--------+
| CustomerNumber | 123456 |
+----------------+--------+
| FirstName | Test |
| MiddleName | Test1 |
| LastName | Test2 |
+----------------+--------+
This is my current sql query:
SELECT
CustomerNumber,
FirstName,
MiddleName,
LastName
FROM Customers
WHERE CustermerNumber = 123456
Is there a way to complete this? I have been looking at transposing it via unpivot but have not been able to understand how.

Answer 1

You can use apply :
select tt.*
from table t cross apply (
values ('CustomerNumber', CustomerNumber), ('FirstName', FirstName),
('MiddleName', MiddleName), ('LastName', LastName)
) tt (name, v);

Answer 2

With dynamic TSQL pivoting you can also manage multiple rows input:
if OBJECT_ID('Test') is not null
drop table [dbo].[Test]
CREATE TABLE [dbo].[Test](CustomerNumber varchar(10), FirstName varchar(10),
MiddleName varchar(10), LastName varchar(10))
--populate test table
insert into [dbo].[Test] values
(123456, 'Test','Test1','Test2')
, (234567, 'Test_2','Test_21','Test_22')
, (345678, 'Test_3','Test_31','Test_32')
--this variable holds all the customer numbers that will become column names
declare #columns nvarchar(max)=''
--this variable contains the dinamically generated TSQL code
declare #sql nvarchar(max)=''
select #columns = #columns + ', [' + [CustomerNumber] + ']' from [dbo].[Test]
set #columns = RIGHT(#columns, len(#columns)-2)
set #sql = #sql + 'select piv.COL as CustomerNumber, ' + #columns
set #sql = #sql + ' from '
set #sql = #sql + ' ( '
set #sql = #sql + ' select [CustomerNumber], col, val, ord '
set #sql = #sql + ' from [dbo].[Test] '
set #sql = #sql + ' CROSS APPLY ('
set #sql = #sql + ' VALUES (''FirstName'' ,FirstName , 1), '
set #sql = #sql + ' (''MiddleName'',MiddleName, 2), '
set #sql = #sql + ' (''LastName'' ,LastName, 3) '
set #sql = #sql + ' )CS (COL,VAL,ORD) '
set #sql = #sql + ' ) src '
set #sql = #sql + ' pivot ( max(val) for [CustomerNumber] in ('+#columns+') ) piv'
set #sql = #sql + ' order by ord'
exec(#sql)
Sample input and output with one row:
Sample input and output with three rows: