Quick Answer: What is the purpose of merge in SQL Server 2008?

What is the purpose of MERGE in SQL?

MERGE statement is used to synchronize two tables by inserting, deleting, and updating the target table rows based on the join condition with the source table.

What is MERGE purpose?

Introduction to the MERGE Statement and SQL Server Data Modification. The MERGE statement is used to make changes in one table based on values matched from anther. It can be used to combine insert, update, and delete operations into one statement.

How does MERGE in SQL work?

The MERGE statement basically works as separate INSERT, UPDATE, and DELETE statements all within the same statement. You specify a “Source” record set and a “Target” table and the JOIN condition between the two.

What is the difference between MERGE and insert in SQL?

MERGE is designed to apply both UPDATE and INSERTs into a target table from a source table. The statement can do both at once, or simply do INSERTs or only UPDATEs. One might even get the impression that INSERT and UPDATE are no longer needed.

Is MERGE a DML command?

Data Manipulation Language (DML) Statements

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INSERT :Use to Add Rows to existing table. UPDATE :Use to Edit Existing Rows in tables. DELETE :Use to Delete Rows from tables. MERGE :Use to Update or Insert Rows depending on condition.

What is the use of merge in Excel?

Merging combines two or more cells to create a new, larger cell. This is a great way to create a label that spans several columns. For example, here cells A1, B1, and C1 were merged to create the label “Monthly Sales” to describe the information in rows 2 through 7.

How do I merge data from one table to another in SQL?

First, you specify the target table and the source table in the MERGE clause. Second, the merge_condition determines how the rows from the source table are matched to the rows from the target table. It is similar to the join condition in the join clause.

How do I MERGE rows in SQL?

The trick here is that the first select ‘main’ selects the rows to display. Then you have one select per field. What is being joined on should be all of the same values returned by the ‘main’ query. if one row has value in field1 column and other rows have null value then this Query might work.

What can I use instead of MERGE in SQL?

The alternative way, which you can use instead of applying the MERGE statement, is to write a sequence of INSERT, UPDATE, and DELETE statements, where, for each row, the decision is made whether to insert, delete, or update the data.

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How do you optimize a query?

It’s vital you optimize your queries for minimum impact on database performance.

  1. Define business requirements first. …
  2. SELECT fields instead of using SELECT * …
  3. Avoid SELECT DISTINCT. …
  4. Create joins with INNER JOIN (not WHERE) …
  5. Use WHERE instead of HAVING to define filters. …
  6. Use wildcards at the end of a phrase only.
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