Often we may need to update a column in a table based of another column in another table.
In SQL Server you can do this using UPDATE statement by joining tables together.
To understand this better let’s take a look at below contrived example.
USE [SqlAndMe]
GO
SELECT CustomerID, Name, OrderAmount
FROM dbo.Customers
GO
SELECT OrderID, CustomerID, Amount
FROM dbo.Orders
GO
Result Set:
CustomerID Name OrderAmount
3 Curtis NULL
4 Lanna NULL
5 Marlin NULL
6 Henry NULL
(4 row(s) affected)
OrderID CustomerID Amount
107 6 8745.00
123 5 4582.00
643 3 5693.00
(3 row(s) affected)
In the above data I want to update OrderAmount column of dbo.Customers with values from Amount column of dbo.Orders.
To achieve this we can use UPDATE statement as below:
UPDATE CUST
SET CUST.OrderAmount = ORDR.Amount
FROM dbo.Customers CUST
INNER JOIN dbo.Orders ORDR ON CUST.CustomerID = ORDR.CustomerID
GO
(3 row(s) affected)
OrderAmount column in dbo.Customers Table is now updated based on JOIN condition.
SELECT CustomerID, Name, OrderAmount
FROM dbo.Customers
GO
CustomerID Name OrderAmount
3 Curtis 5693.00
4 Lanna NULL
5 Marlin 4582.00
6 Henry 8745.00
(4 row(s) affected)
I have used a simple example here to explain the concept easily
Hope This Helps!
Vishal
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Filed under: SQLServer, SQLServer 2005, SQLServer 2008, SQLServer 2008 R2, SQLServer 2012, Working With Data Image may be NSFW.
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