Merge, join, concatenate and compare

Use concat() to merge multiple Series or DataFrame objects along a shared axis, accepting a list or dict of homogeneously-typed inputs while optionally applying set logic (union or intersection) to indexes on other axes. For column-based combinations, employ DataFrame.join(). To update missing values with existing non-missing counterparts at identical locations, utilize DataFrame.combine_first(). Combine two objects using SQL-style logic via merge(), align along an ordered axis with merge_ordered(), or match by proximity rather than exact keys using merge_asof(). Finally, identify value discrepancies between two Series or DataFrames by calling Series.compare() or DataFrame.compare(). Scope: pandas. Reviewed October 4, 2026.