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layout language permalink command related_commands
eq_join outer_join zip

Command syntax

{% apibody %} sequence.inner_join(other_sequence, predicate_function) → stream array.inner_join(other_sequence, predicate_function) → array {% endapibody %}


Returns an inner join of two sequences.

The returned sequence represents an intersection of the left-hand sequence and the right-hand sequence: each row of the left-hand sequence will be compared with each row of the right-hand sequence to find all pairs of rows which satisfy the predicate. Each matched pair of rows of both sequences are combined into a result row. In most cases, you will want to follow the join with zip to combine the left and right results.

{% infobox %} Note that inner_join is slower and much less efficient than using eq_join or concat_map with get_all. You should avoid using inner_join in commands when possible. {% endinfobox %}

Example: Return a list of all matchups between Marvel and DC heroes in which the DC hero could beat the Marvel hero in a fight.

    lambda marvel_row, dc_row: marvel_row['strength'] < dc_row['strength']

(Compare this to an outer_join with the same inputs and predicate, which would return a list of all Marvel heroes along with any DC heroes with a higher strength.)

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