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Friday, November 14, 2014

SQL Important Queries Part 3

Nth Highest Salary In SQL Server :

SELECT * FROM (select row_number() over(order by salary desc) as rowno, SALARY from tblsalary GROUP BY SALARY) AS A
WHERE A.rowno = 3

SELECT * FROM tblsalary ORDER BY SALARY DESC

USING MERGE Query in SQL Server :

--Create a target table
CREATE TABLE Products
(
ProductID INT PRIMARY KEY,
ProductName VARCHAR(100),
Rate MONEY
)
GO
--Insert records into target table
INSERT INTO Products
VALUES
(1, 'Tea', 10.00),
(2, 'Coffee', 20.00),
(3, 'Muffin', 30.00),
(4, 'Biscuit', 40.00)
GO
--Create source table
CREATE TABLE UpdatedProducts
(
ProductID INT PRIMARY KEY,
ProductName VARCHAR(100),
Rate MONEY
)
GO
--Insert records into source table
INSERT INTO UpdatedProducts
VALUES
(1, 'Tea', 10.00),
(2, 'Coffee', 25.00),
(3, 'Muffin', 35.00),
(5, 'Pizza', 60.00)
GO
SELECT * FROM Products
SELECT * FROM UpdatedProducts
GO

--Synchronize the target table with refreshed data from source table
MERGE Products AS TARGET
USING UpdatedProducts AS SOURCE
ON (TARGET.ProductID = SOURCE.ProductID)

--When records are matched, update the records if there is any change
WHEN MATCHED AND TARGET.ProductName <> SOURCE.ProductName
OR TARGET.Rate <> SOURCE.Rate THEN
UPDATE SET TARGET.ProductName = SOURCE.ProductName,
TARGET.Rate = SOURCE.Rate

--When no records are matched, insert the incoming records from source table to target table
WHEN NOT MATCHED BY TARGET THEN
INSERT (ProductID, ProductName, Rate)
VALUES (SOURCE.ProductID, SOURCE.ProductName, SOURCE.Rate)

--When there is a row that exists in target table and same record does not exist in source table
--then delete this record from target table
WHEN NOT MATCHED BY SOURCE THEN
DELETE
--$action specifies a column of type nvarchar(10)
--in the OUTPUT clause that returns one of three
--values for each row: 'INSERT', 'UPDATE', or 'DELETE',
--according to the action that was performed on that row
OUTPUT $action,
DELETED.ProductID AS TargetProductID,
DELETED.ProductName AS TargetProductName,
DELETED.Rate AS TargetRate,
INSERTED.ProductID AS SourceProductID,
INSERTED.ProductName AS SourceProductName,
INSERTED.Rate AS SourceRate;
SELECT @@ROWCOUNT;
GO

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