دستور OVER PARTITION در SQL

SELECT TOP 100 AVG(Quantity) AS Quantity,
               MAX(Price)    AS Price
FROM [dbo].Decision;

SELECT TOP 100 CustomerId,
               AVG(Quantity) AS Quantity,
               MAX(Price)    AS Price
FROM [oms.tse.new].Decision;

SELECT TOP 100 CustomerId,
               AVG(Quantity) OVER (PARTITION BY CustomerId)     AS Quantity,
               MAX(Price) OVER (PARTITION BY CustomerId)        AS Price,
               COUNT(CustomerId) OVER (PARTITION BY CustomerId) AS Count
FROM [dbo].Decision;

SELECT TOP 100 CustomerId,
               AVG(Quantity) OVER (PARTITION BY CustomerId)                AS AvgQuantity,
               MAX(Price) OVER (PARTITION BY CustomerId)                   AS MaxPrice,
               COUNT(CustomerId) OVER (PARTITION BY CustomerId)            AS Count,
               ROW_NUMBER() OVER (PARTITION BY Channel ORDER BY Id ASC) AS RowNumber
FROM [dbo].Decision;