What does a left outer join retain in ArcGIS Pro?

In ArcGIS Pro, a left outer join retains both the target records and the matching records from the join table. This means that for every record from the target layer, the join operation will include the corresponding matching records from the joined layer. If there is no match for a target record, the output will still include that target record but will fill in the missing attributes from the join table with null values.

This is a vital functionality in data analysis as it allows users to retain the complete set of data from the primary dataset while also incorporating related information from the secondary dataset where available. This is particularly useful in scenarios where you want to analyze and report on all items in your primary dataset, regardless of whether those items have correspondences in the secondary dataset.

Understanding this process is essential for effective data analysis in ArcGIS Pro, as it influences how users construct their data relationships and interpret results in their maps and tables.