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Learn how spatial joins match features by location, how spatial predicates determine which features match, and why one feature can sometimes join to several others.
Learn why spatial joins can produce repeated records, how to distinguish legitimate multiple matches from true duplicates, and what to check before deleting rows.
Learn how one-to-one and one-to-many spatial joins handle multiple geographic matches, why one-to-many results can increase row counts, and what is lost when several matches are collapsed into one.
Learn how Within, Contains, and Intersects differ in GIS, why Within and Contains depend on direction, and why features on boundaries often behave differently from features in polygon interiors.
Learn the difference between spatial and attribute joins, when geographic relationships should be used as the join condition, and why reliable shared identifiers are often preferable when they exist.