Tutorial by Topics: merge

MERGE (often also called UPSERT for "update or insert") allows to insert new rows or, if a row already exists, to update the existing row. The point is to perform the whole set of operations atomically (to guarantee that the data remain consistent), and to prevent communication overhead for multiple SQL statements in a client/server system.

Starting with SQL Server 2008, it is possible to perform insert, update, or delete operations in a single statement using the MERGE statement.

The MERGE statement allows you to join a data source with a target table or view, and then perform multiple actions against the target based on the results of that join.

A join combines two tables containing related columns. The term covers a wide range of operations, essentially everything except appending the two tables. "Merge" is a synonym. Type ?`[.data.table` for the official docs.

How to merge cells

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