I have 2 datasets, a and b which I am merging using a left join. Table a has duplicate join keys, but b does not. When I complete the join I am ending up with more records in a than before. I know the duplicate keys are a problem but they are not something I can change. However, I don't understand WHY they are causing the issue. My understanding is that in cases of duplicate keys in the left table (a), the corresponding key in the right table (b) will simply match to both occurrences in a, without creating an extra records? Where am I going wrong here? Thanks.
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