Friday 22 May 2015

How to Transform rows into columns in sql server

to create the table
Create Table Countries
(
     Country nvarchar(50),
     City nvarchar(50)
)
GO

Insert into Countries values ('USA','New York')
Insert into Countries values ('USA','Houston')
Insert into Countries values ('USA','Dallas')

Insert into Countries values ('India','Hyderabad')
Insert into Countries values ('India','Bangalore')
Insert into Countries values ('India','New Delhi')

Insert into Countries values ('UK','London')
Insert into Countries values ('UK','Birmingham')
Insert into Countries values ('UK','Manchester')

Here is the interview question:
Write a sql query to transpose rows to columns. The output should be as shown below.
 
 


Using PIVOT operator we can very easily transform rows to columns

Select Country, City1, City2, City3
From
(
  Select Country, City,
    'City'+
      cast(row_number() over(partition by Country order by Country)
             as varchar(10)) ColumnSequence
  from Countries
) Temp
pivot
(
  max(City)
  for ColumnSequence in (City1, City2, City3)

) Piv

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