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course: ksqlDB 101

Splitting Two Streams with ksqlDB

2 min
Allison

Allison Walther

Integration Architect (Presenter)

Robin Moffatt

Robin Moffatt

Principal Developer Advocate (Author)

Splitting Two Streams with ksqlDB

You can perform the inverse of merging streams with ksqlDB: you can split them. By specifying a predicate on a field in the data, you can route messages to different target streams.

Take the example of a stream of orders for all countries:

orders-for-all-countries

You may want to split these orders for country-specific processing:

orders-combined

To do this in ksqlDB, use SQL statements with appropriate predicates:

CREATE STREAM ORDERS_US AS
   SELECT * FROM ORDERS_COMBINED
   WHERE SOURCE = 'US';

CREATE STREAM ORDERS_UK AS
   SELECT * FROM ORDERS_COMBINED
   WHERE SOURCE = 'UK';

CREATE STREAM ORDERS_OTHER AS
   SELECT * FROM ORDERS_COMBINED
   WHERE SOURCE != 'US'
   AND SOURCE != 'UK';

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Total 28

  1. Introduction to ksqlDB
    2 min
  2. Interacting with ksqlDB
    2 min
  3. Hands On: Interacting with ksqlDB
    5 min
  4. Creating, Exporting, and Importing Data
    2 min
  5. Filtering with ksqlDB
    1 min
  6. Hands On: Filtering with ksqlDB
    1 min
  7. Lookups and Joins with ksqlDB
    2 min
  8. Hands On: Lookups and Joins with ksqlDB
    2 min
  9. Transforming Data with ksqlDB
    2 min
  10. Hands On: Transforming Data with ksqlDB
    2 min
  11. Flatten Nested Records with ksqlDB
    1 min
  12. Hands On: Flatten Nested Records with ksqlDB
    2 min
  13. Converting Data Formats with ksqlDB
    2 min
  14. Hands On: Converting Data Formats with ksqlDB
    2 min
  15. Merging Two Streams with ksqlDB
    1 min
  16. Hands On: Merging Two Streams with ksqlDB
    2 min
  17. Splitting Two Streams with ksqlDB
    2 min
  18. Hands On: Splitting Two Streams with ksqlDB
    2 min
  19. Streams and Tables
    2 min
  20. Stateful Aggregations (Materialized Views)
    2 min
  21. Hands On: Stateful Aggregations (Materialized Views)
    2 min
  22. Push Queries and Pull Queries
    2 min
  23. Hands On: Push Queries and Pull Queries
    2 min
  24. Under the Covers of ksqlDB
    2 min
  25. ksqlDB Code Lifecycle
    2 min
  26. Apply Lambda Functions to Arrays and Maps
    2 min
  27. Hands On: Apply Lambda Functions to Arrays and Maps
    2 min
  28. Monitoring ksqlDB
    1 min

Related Resources

Presentation

Inside ksqlDB

Tutorial

How to Split a Stream of Events into Substreams

Video

ksqlDB HOWTO: Split and Merge Kafka Topics

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Splitting Two Streams with ksqlDB

Hi, I'm Allison Walther with Confluent. In this lesson, we'll be talking about splitting streams with ksqlDB. KsqlDB's create stream as feature allows us to create many different views of our data. We can create streams from a sub-set of events in another stream, or from a combination of events in multiple streams and/or tables. This feature makes it easy to split a stream of events based on some criteria. Here, we create one stream with a select that is only getting US orders, and we create another stream with a select for UK orders. Now, US and UK-specific applications can read from streams that are custom-built for them and not have to worry about filtering out events that don't apply. That's a wrap on this lesson. Let's jump into splitting streams in an exercise.