Merge

Merge is the act of combining two or more distinct items into a single unit. The term is used across disciplines to describe the integration of data, files, software changes, or organizational entities. A successful merge preserves essential properties of the inputs while creating a unified whole and resolves conflicts where inputs disagree.

In software development and version control, merging combines changes from different branches or forks. A merge operation produces a new version that incorporates edits from multiple sources. When changes touch the same part of a file, a merge conflict may occur and must be resolved by a human or automated tool. Techniques include merge commits, rebasing, and various workflow conventions to manage history and conflict resolution.

In data processing and databases, a merge combines datasets by aligning rows based on keys or indices. Common operations include inner, left, right, and full outer merges, which correspond to SQL joins. The SQL MERGE statement can perform conditional insert, update, or delete based on source data. Programming libraries offer merge or join functions (for example, DataFrame.merge) to implement these patterns.

In business contexts, a merger is a corporate action where two or more companies combine into a single entity, often to gain scale, diversify operations, or increase market share. Mergers may be voluntary or subject to regulatory approval and typically require due diligence, integration planning, and governance changes.

Challenges of merging include data incompatibilities, conflicting records, and cultural or operational integration. Effective merging relies on clear matching criteria, data governance, documentation of decisions, and processes for testing and rollback. Related concepts include concatenation, joining, and data integration.