Joins in DataFrames
Explore how to join pandas DataFrames using the merge method, including inner, outer, left, and right joins. Understand how to align data on columns, handle mismatched data with NaN, and use parameters like indicator and validate to manage join outcomes and ensure data integrity.
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Joins
Databases have different types of joins. The four common ones include inner, outer, left, and right. The DataFrame has two methods to support these operations, join and merge. It’s preferred to use the merge method.
Note: The
joinmethod is meant for joining based on the index rather than columns. In practice, joining is usually based on columns instead of index values.
If we want thejoinmethod to join based on column values, we need to set that column as the index first:
df1.set_index('name').join(df2.set_index('name'))
It’s easier to just use themergemethod.
The default join type for the merge method is an inner join. ...