Difference between Append and Merge data

Question

What is the difference between Appnend and Merge in SQL server database?

Jaish Mathews · Answer

I collected a tabular represenation of this from another source. Here’s a tabular representation of the differences between Append and Merge in a SQL Server database: Feature Append Merge Definition Adds new rows to a table without modifying existing data. Combines datasets by inserting, updating, or deleting rows in the target table based on conditions. Use Case Used when you need to add additional rows from one table to another. Used when you need to synchronize or reconcile differences between two datasets. Effect on Data Only inserts new rows into the table. Performs INSERT, UPDATE, or DELETE operations depending on specified conditions. Primary Statement INSERT INTO ... SELECT ... MERGE INTO ... USING ... ON ... WHEN MATCHED ... WHEN NOT MATCHED ... Existing Data Does not affect existing rows in the target table. Can modify (update/delete) existing rows and add new rows. Complexity Relatively simple operation. More complex, with multiple conditions and actions. Performance Typically faster as it involves only inserting data. Can be slower due to conditional logic and multiple potential operations (INSERT, UPDATE, DELETE). Conflict Handling No handling for conflicts, assumes no duplicates or overlap in target data. Can handle conflicts using WHEN MATCHED and WHEN NOT MATCHED clauses. Typical Scenario Appending historical data to a log or archive table. Keeping a target table (e.g., a staging or final table) in sync with a source dataset. Append Example This example appends data from SourceTable to TargetTable . -- APPEND operation: Insert all rows from SourceTable into TargetTable INSERT INTO TargetTable (Column1, Column2, Column3) SELECT Column1, Column2, Column3 FROM SourceTable; Merge Example This example synchronizes data between SourceTable and TargetTable . Rows are: Updated if they match. Inserted if they don't exist. Deleted if they are missing in the source. -- MERGE operation: Synchronize SourceTable with TargetTable MERGE INTO TargetTable AS Target USING SourceTable AS Source ON Target.ID = Source.ID -- Matching condition (e.g., primary key) WHEN MATCHED THEN UPDATE SET Target.Column1 = Source.Column1, Target.Column2 = Source.Column2 WHEN NOT MATCHED BY TARGET THEN INSERT (ID, Column1, Column2) VALUES (Source.ID, Source.Column1, Source.Column2) WHEN NOT MATCHED BY SOURCE THEN DELETE; -- Optional: You can output changes for verification OUTPUT $action, inserted.*, deleted.*;

Amit Mohanty · Answer

In SQL Server, append means adding new rows to the table by using INSERT and does not check or change any data. It is easy and great for adding data. This operation merges data from a source and target table. It is an advanced operation because it allows conditional actions like INSERT, UPDATE, or DELETE based on a match condition, hence suitable for data synchronization. Use Append for easy data additions and Merge for complicated situations with several operations. Key Differences: Feature Append ( INSERT ) Merge Operation Scope Only adds new rows Can add, update, or delete rows Data Check No check for duplicates Checks data based on condition Complexity Simple syntax Complex syntax Flexibility Limited Highly flexible Performance Fast for bulk inserts Slower due to conditional checks Best Use Case Adding new data Synchronizing tables or handling conditional updates You can choose Append (INSERT) for straightforward data additions and Merge when working with more complex data synchronization needs.

Jayraj Chhaya · Answer

Hi In SQL Server, the terms "Append" and "Merge" refer to different operations for handling data within tables. Append typically involves adding new rows to an existing table. This can be achieved using the INSERT statement. For example: INSERT INTO TargetTable (Column1, Column2) VALUES (Value1, Value2); This operation simply adds new records without altering existing ones. On the other hand, Merge is a more complex operation that allows you to perform insert, update, or delete actions based on the comparison of two datasets. The MERGE statement is particularly useful for synchronizing two tables. MERGE INTO TargetTable AS target USING SourceTable AS source ON target.ID = source.ID WHEN MATCHED THEN UPDATE SET target.Column1 = source.Column1 WHEN NOT MATCHED THEN INSERT (Column1, Column2) VALUES (source.Column1, source.Column2); While Append is about adding new data, Merge provides a comprehensive way to synchronize and manage data between two tables.

Muhammad Imran Ansari · Answer

Hi Kiran, Yes, SQL Server supports the MERGE statement, which allows you to perform operations like INSERT, UPDATE, and DELETE in a single query by comparing a target table with a source table. It’s commonly used for scenarios like data synchronization. On your second query regarding append Operation, for appending rows from one table to another, you typically use the INSERT INTO statement. You cannot use UNION or UNION ALL directly to append rows from one table to another. UNION combines results from multiple queries into a single dataset, which is useful for querying but doesn’t modify the target table. When using INSERT INTO ... SELECT, the columns selected from the source table must align with the target table's column order, unless you explicitly specify the column names in both the INSERT INTO and SELECT clauses. Thank you!

Kiran Kumar · Answer

Thank you for all responses As you mentioned Merge is a keyword in database we can get the feature of merging tables , but do we have this syntax in MS SQL server Append meaning adding new rows into a table from another tab Here, I have a question can we user union and union all for this append instead of Insert into table script Do we need to have column position same as the source table from traget

Muhammad Imran Ansari · Answer

Hi Kiran, Append and Merge are not explicit SQL commands in SQL Server. However, these are often used in database operations to describe different actions. Append: This refers to adding data to an existing table without modifying or checking existing rows. A common example is the INSERT command. INSERT INTO TargetTable (Column1, Column2, ....., ColumnN) SELECT Column1, Column2, ....., ColumnN FROM SourceTable Merge: This is a combination of INSERT, UPDATE, and DELETE operations into a single statement. A comomn example is the MERGE statement. Here is a simple example of a Merge: Target Table: Name ID Name Age 1 Alice 25 2 Bob 30 Source Table: ID Name Age 2 Bob Updated 35 3 Charlie 22 MERGE INTO TargetTable AS Target USING SourceTable AS Source ON Target.ID = Source.ID WHEN MATCHED THEN UPDATE SET Target.Name = Source.Name, Target.Age = Source.Age WHEN NOT MATCHED THEN INSERT (ID, Name, Age) VALUES (Source.ID, Source.Name, Source.Age); Thank you!

Difference between Append and Merge data

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