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Joining Datasets with KSQL

KSQL provides a SQL-like interface for most of the operations you perform using Kafka Streams. Like Kafka Streams, KSQL is capable of joining multiple streams into a single dataset. In this lab, we will work with joins in KSQL by writing a persistent streaming query that joins two streams. This will give you some hands-on experience with joins in KSQL.

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Path Info

Clock icon Intermediate
Clock icon 30m
Clock icon Oct 18, 2019

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Table of Contents

  1. Challenge

    Create Streams for Both Input Topics

    1. Start a KSQL session:

      sudo ksql
    2. Set auto.offset.reset to earliest so that all streams will process the existing test data:

      SET 'auto.offset.reset' = 'earliest';
    3. View the data in the member_signups topic:

      PRINT 'member_signups' FROM BEGINNING;
    4. Create a stream for the member_signups topic:

      CREATE STREAM member_signups
        (lastname VARCHAR,
          firstname VARCHAR)
        WITH (KAFKA_TOPIC='member_signups',
    5. View the data in the member_contact topic:

      PRINT 'member_contact' FROM BEGINNING;
    6. Create a stream for the member_contact topic:

      CREATE STREAM member_contact
        (email VARCHAR)
        WITH (KAFKA_TOPIC='member_contact',
  2. Challenge

    Create a Persistent Streaming Query to Join the Two Streams and Output the Result

    1. Create a persistent streaming query to join the two streams:

      CREATE STREAM member_email_list AS
        SELECT member_signups.firstname, member_signups.lastname,
        FROM member_signups
        INNER JOIN member_contact WITHIN 365 DAYS ON member_signups.rowkey = member_contact.rowkey;
    2. Check the output topic to verify the correct data is present:


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