SQL Pivot Table (English)

Make SQL Pivot Table

Pivot Table is result data table from transaction data is processed by Aggregate function (Ex. Sum, Avg, Max, Min) Pivot table is use for analyst each point of view. For easy to understand it. We see example now.

This structur table contains.
SellerName : Name of Seller.
InvoiceNO : No of invoice or bill.
InvoiceDate : Date of Invoice or bill.
Amount : Total circulation of Invoice.

Assume We have question is we look for sales volume of each seller and separate by month.
General query we maybe with WHERE MONTH(InvoiceDate) = 1 , WHERE MONTH(InvoiceDate) = 2 til complete And maybe use GROUP BY Together.

Example Query Month = 1 Only
SELECT SellerName,SUM(Amount) as Amount
  FROM InvoiceList
  WHERE 
  MONTH(InvoiceDate)=1

  GROUP BY SellerName 

View of report is not comfortable to analyst because we will use
several month table. For comfortable to analyst we should use PIVOT

Example Query Pivot 
SELECT * FROM
(SELECT MONTH(InvoiceDate) as Month, Amount ,SellerName 
FROM InvoiceList
) as SourceTable
PIVOT
(
SUM(Amount) for SellerName in (Dang,Dum,Jumpee,SreeDa)

) as PV

*** Next problem is null value on the table. Focus at month 1 of Dum It has Null because all of month 1 Dum not have circulation. If we use this query on program maybe found error. We can use ISNULL for improve our query.

SELECT Month 

, ISNULL(Dang,0) as Dang 

, ISNULL(Dum,0) as Dum 

, ISNULL(Jumpee,0) as Jumpee 

, ISNULL(SreeDa,0) as SreeDa 

 FROM

(SELECT MONTH(InvoiceDate) as Month, Amount ,SellerName 

FROM InvoiceList

) as SourceTable

PIVOT

(

SUM(Amount) for SellerName in (Dang,Dum,Jumpee,SreeDa)

) as PV

After Improve query...