MERGE Statement in SQL Server

MERGE is a new feature introduce in SQL server 2008 version that provides an efficient way to perform multiple DML operations. In previous versions of SQL Server, we had to write separate statements to INSERT, UPDATE, or DELETE data based on certain conditions, but now, using MERGE statement, we can include the logic of such data modifications in one statement that even checks when the data is matched, then just update it, and when unmatched, insert it. One of the most important advantages of MERGE statement is all the data is read and processed only once.

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Manipulating data in a single query for below parameters

·         Insert the records if the record does not exists.

·         Update the records if exists.

·         Delete the record if exists.

Now we will write MERGE process for tables created earlier. We will make sure that we will have our three conditions discussed above are satisfied.