pivot trong SQL Server

Pivot đơn giản là kỹ thuật trình bày hàng thành cột trong SQL Server.

http://blog.sqlauthority.com/2008/06/07/sql-server-pivot-and-unpivot-table-examples/

Nếu muốn dùng Dynamic pivot:

http://www.mssqltips.com/sqlservertip/2783/script-to-create-dynamic-pivot-queries-in-sql-server/

DECLARE @columns NVARCHAR(MAX), @sql NVARCHAR(MAX);
SET @columns = N'';
SELECT @columns += N', p.' + QUOTENAME(Name)
  FROM (SELECT p.Name FROM dbo.Products AS p
  INNER JOIN dbo.OrderDetails AS o
  ON p.ProductID = o.ProductID
  GROUP BY p.Name) AS x;
SET @sql = N'
SELECT ' + STUFF(@columns, 1, 2, '') + '
FROM
(
  SELECT p.Name, o.Quantity
   FROM dbo.Products AS p
   INNER JOIN dbo.OrderDetails AS o
   ON p.ProductID = o.ProductID
) AS j
PIVOT
(
  SUM(Quantity) FOR Name IN ('
  + STUFF(REPLACE(@columns, ', p.[', ',['), 1, 1, '')
  + ')
) AS p;';
PRINT @sql;
EXEC sp_executesql @sql;

http://www.mssqltips.com/sqlservertip/1455/using-the-case-expression-instead-of-dynamic-sql-in-sql-server/