Skip to main content

MERGE in SQL SERVER -INSERT, UPDATE, DELETE in single execution.

To do multiple DML operations in SQL SERVER we use MERGE, that a strong feature of SQL SERVER, In earlier versions of SQL SERVER we had to write separate statement for INSERT, UPDATE, DELETE, now by using MERGE we can perform INSERT, UPDATE, DELETE in one statement by checking data, if data matched then update otherwise insert or in particular condition we can also delete.
Note-Merge statement read entire data and processed only one.
The Merge query is given below:
Suppose there are two tables, Table1 and table2, table1 contains data about books like ISBN, Title, quantity, price, etc.. and table2 contains updated data of book so here we need to update Table1 from Table2, Table may have new records or updated records(like quantity, price etc ) or it may be some records should be delete from Table1.
CREATE  TABLE TABLE1
(
biBookId BIGINT IDENTITY(1,1),
vIsbn VARCHAR(20),
iQty INT,
dcPrice DECIMAL(18,2)
)
CREATE  TABLE TABLE2
(
biBookId BIGINT IDENTITY(1,1),
vIsbn VARCHAR(20),
iQty INT,
dcPrice DECIMAL(18,2)
)
/*insert some data in table1*/
INSERT INTO TABLE1(vIsbn,iQty,dcPrice) VALUES('9987876543343',10,0.00)
INSERT INTO TABLE1(vIsbn,iQty,dcPrice) VALUES('8898576476532',1,21.30)
INSERT INTO TABLE1(vIsbn,iQty,dcPrice) VALUES('9898765456763',50,4.00)
INSERT INTO TABLE1(vIsbn,iQty,dcPrice) VALUES('8987655663452',0,5.00)
/*insert some data in table2*/
INSERT INTO TABLE2(vIsbn,iQty,dcPrice) VALUES('9987876543343',20,0.00)
INSERT INTO TABLE2(vIsbn,iQty,dcPrice) VALUES('8898576476532',1,31.30)
INSERT INTO TABLE2(vIsbn,iQty,dcPrice) VALUES('9898765456763',5,4.00)
INSERT INTO TABLE2(vIsbn,iQty,dcPrice) VALUES('8987655663452',0,15.00)
INSERT INTO TABLE2(vIsbn,iQty,dcPrice) VALUES('8987655663451',11,25.00)
/*data in table1 before merge*/
select * from TABLE1
/*MERGE statement*/
MERGE TABLE1 AS tbl1
USING (SELECT  vIsbn,iQty,dcPrice FROM TABLE2) as tbl2
ON tbl1.vIsbn=tbl2.vIsbn
WHEN MATCHED AND tbl2.iQty=0 THEN DELETE
WHEN MATCHED THEN UPDATE
SET tbl1.iQty=tbl2.iQty,
tbl1.dcPrice=tbl2.dcPrice
WHEN NOT MATCHED THEN
INSERT(vIsbn,iQty,dcPrice)
VALUES(tbl2.vIsbn, tbl2.iQty, tbl2.dcPrice);
GO
SELECT * FROM TABLE1
DROP TABLE TABLE1
DROP TABLE TABLE2

Popular posts from this blog

What is difference between UNION and UNION ALL in SQL Server

We use UNION and UNION ALL operator to combine multiple results set into one result set.
UNION operator is used to combining multiple results set into one result set but removes any duplicate rows. Basically, UNION is used to performing a DISTINCT operation across all columns in the result set. UNION operator has the extra overhead of removing duplicate rows and sorting result.
UNION ALL operator use to combine multiple results set into one result set but it does not remove any duplicate result. Actually, this does not remove duplicate rows so it is faster than the UNION operator. If you want to combine multiple results and without duplicate records then use UNION otherwise UNION ALL is better.
Following some rules for using UNION/UNION ALL operator
1.The number of the column should be the same in the query's when you want to combine them. 2.The column should be of the same data type. 3.ORDER BY clause can be applied to the overall result set not within each result set.
4.Column name of …

Add day to ISODate in MongoDB

We can use $add operator to add days in ISODate in mongodb, $add is the Arithmetic Aggregation Operator which adds number and date in mongodb.
Syntax:

{ $add: [ <expression1>, <expression2>, ... ] }

Note:  If one of the argument is date $add operator treats to other arguments as milliseconds to add to the date.
Example: Suppose we have a Test collection as below.

{"Title" : "Add day to ISODate in MongoBD","CreatedDate" : ISODate("2016-07-07T08:00:00.000Z")}

Query to add 2 days in CreatedDate

db.Test.aggregate([      { $project: { Title: 1, AddedDate: { $add: [ "$CreatedDate", 2*24*60*60000 ] } } }    ])

Result:

{ "_id" : ObjectId("579a1567ac1b3f3732483de0"), "Title" : "Add day to ISODate in MongoBD", "AddedDate" : ISODate("2016-07-09T08:00:00.000Z") }

Note: As mentioned in above note we have to convert days in millisecond because $add operator treat to other arg…

Merge and Merge join transformation in SSIS

MERGE TRANSFORMATION
Using Merge Transformation we can combine two sorted data-set into single data-set basically Merge Transformation used to combines rows from two sorted data flows into one sorted data flow. Following tasks you may perform using Merge Transformation: 1.Suppose we have a scenario like, we need to merge data from a database table and excel means we want to merge data from two different data sources. For such type of scenario, you can use Merge Transformation. 2.If we want to merge data from two same structured tables but exists two different servers. 3.Sometimes we get an error due to data in a row, after correcting errors in the data we can re-merge rows easily. See below explanations may help you to understand Merge Transformation: I do evaluate here, you already know about the data source, data conversion, data flow, task flow, control flow etc. Note:Before Merge transformation, we need to sort the data using Sort Transformation. After sorting data add data path to Merge…