# ksqlDB **URL:** https://forum.confluent.io/c/stream-processing/ksqldb/11.md [Latest](https://forum.confluent.io/latest.md) · [Categories](https://forum.confluent.io/categories.md) --- ## [What is ksqlDB?](https://forum.confluent.io/t/what-is-ksqldb/88)
**Author:** [@rmoff](https://forum.confluent.io/u/rmoff)\ **Replies:** 0\ **Last updated:** [12 November 2020 17:58 UTC](https://forum.confluent.io/t/what-is-ksqldb/88 "2020-11-12T17:58:37Z")
ksqlDB is an event streaming database. What exactly does that mean? An event streaming database is a particular kind of database that helps you build stream processing apps. It consolidates the many components found in … --- ## [About the ksqlDB category](https://forum.confluent.io/t/about-the-ksqldb-category/19)
**Author:** [@rmoff](https://forum.confluent.io/u/rmoff)\ **Replies:** 0
ksqlDB is the event streaming database purpose-built for stream processing applications. It’s available both as a managed service in Confluent Cloud, or you can run it yourself. --- ## [ksqlDB JSON\_SR with existing KEY\_SCHEMA\_ID fails on structured key: Incompatible schema of type JSON / id.compatibility.strict](https://forum.confluent.io/t/ksqldb-json-sr-with-existing-key-schema-id-fails-on-structured-key-incompatible-schema-of-type-json-id-compatibility-strict/38374)
**Author:** [@Ethan2029](https://forum.confluent.io/u/Ethan2029)\ **Replies:** 0\ **Last updated:** [17 May 2026 11:45 UTC](https://forum.confluent.io/t/ksqldb-json-sr-with-existing-key-schema-id-fails-on-structured-key-incompatible-schema-of-type-json-id-compatibility-strict/38374 "2026-05-17T11:45:44Z")
Hi Confluent community, I am looking for advice on a ksqlDB / JSON\_SR / Schema Registry issue. Context We have the following flow: Source topic: raw JSON, no Schema Registry ksqlDB: transforms the payload into the ta… --- ## [KSQLDB Processing Time](https://forum.confluent.io/t/ksqldb-processing-time/38102)
**Author:** [@Metalmania97](https://forum.confluent.io/u/Metalmania97)\ **Replies:** 0\ **Last updated:** [13 September 2025 05:52 UTC](https://forum.confluent.io/t/ksqldb-processing-time/38102 "2025-09-13T05:52:55Z")
Hello. I am trying to test the processing delay introduced by KSQLDB and I need the processing timestamp to do this. As I understand ROWTIME is the timestamp of the kafka record. Is there a way to insert a processing ti… --- ## [Using Json Value\_format in KsqlDB I can see the topic messages null in stream](https://forum.confluent.io/t/using-json-value-format-in-ksqldb-i-can-see-the-topic-messages-null-in-stream/38096)
**Author:** [@Vidya\_Babar](https://forum.confluent.io/u/Vidya_Babar)\ **Replies:** 0\ **Last updated:** [29 August 2025 10:45 UTC](https://forum.confluent.io/t/using-json-value-format-in-ksqldb-i-can-see-the-topic-messages-null-in-stream/38096 "2025-08-29T10:45:07Z")
Using Value\_format JSON in KsqlDB I can see the topic messages null in stream using JSON Schema cloud you please tell me the reason and solution. I can see the topic messages using Value\_Format Kafka but COUNT and GRO… --- ## [Running a select query throwing error in control center console](https://forum.confluent.io/t/running-a-select-query-throwing-error-in-control-center-console/37970)
**Author:** [@nitin-kunal](https://forum.confluent.io/u/nitin-kunal)\ **Replies:** 0\ **Last updated:** [16 July 2025 03:31 UTC](https://forum.confluent.io/t/running-a-select-query-throwing-error-in-control-center-console/37970 "2025-07-16T03:31:09Z")
step 1 :I am using this URL to download Quick Start for Confluent Platform | Confluent Documentation step 2: got to: cd cp-all-in-one/cp-all-in-one step 3: docker compose up -d got to ksql step5: CREATE STREAM MOVE… --- ## [Adding in Strimzi Callback Handler](https://forum.confluent.io/t/adding-in-strimzi-callback-handler/37843)
**Author:** [@kerwnshaw](https://forum.confluent.io/u/kerwnshaw)\ **Replies:** 0\ **Last updated:** [27 May 2025 18:37 UTC](https://forum.confluent.io/t/adding-in-strimzi-callback-handler/37843 "2025-05-27T18:37:19Z")
Our team is looking at setting up ksqlDB with our on-premise deployment of Kafka. We use Strimzi to handle our OAuth and will need to add in the jar file that contains all the classes we need in order to do this. Does an… --- ## [ARM64 container image?](https://forum.confluent.io/t/arm64-container-image/37724)
**Author:** [@chainhead](https://forum.confluent.io/u/chainhead)\ **Replies:** 0\ **Last updated:** [2 May 2025 16:56 UTC](https://forum.confluent.io/t/arm64-container-image/37724 "2025-05-02T16:56:44Z")
When do you plan to release confluentinc/ksqldb-server for ARM64? I don’t see any ARM64 tags here. I plan to run Kafka and KSQL container images on EC2 instances with Graviton processor. Seems like I am forced to go to … --- ## [ksqlDB not starting locally](https://forum.confluent.io/t/ksqldb-not-starting-locally/37528)
**Author:** [@nikolai](https://forum.confluent.io/u/nikolai)\ **Replies:** 3\ **Last updated:** [19 March 2025 21:32 UTC](https://forum.confluent.io/t/ksqldb-not-starting-locally/37528 "2025-03-19T21:32:57Z")
I want to run a kafka cluster locally to test some code I ran ○ confluent local services start and I got the following error: The local commands are intended for a single-node development environment only, NOT for prod… --- ## [Ksqldb table key and value with avro schema serialization error](https://forum.confluent.io/t/ksqldb-table-key-and-value-with-avro-schema-serialization-error/37434)
**Author:** [@NikkiZ](https://forum.confluent.io/u/NikkiZ)\ **Replies:** 0\ **Last updated:** [7 March 2025 17:51 UTC](https://forum.confluent.io/t/ksqldb-table-key-and-value-with-avro-schema-serialization-error/37434 "2025-03-07T17:51:38Z")
Hi, I created a topic and register Avro schema for the Key and Value. They are both objects. I also verified the schema is registed in the schema registery. Then create a source table in the Ksqldb with below query to p… --- ## [ksqlDB is not starting](https://forum.confluent.io/t/ksqldb-is-not-starting/37140)
**Author:** [@hiraneranda](https://forum.confluent.io/u/hiraneranda)\ **Replies:** 5\ **Last updated:** [10 February 2025 13:40 UTC](https://forum.confluent.io/t/ksqldb-is-not-starting/37140 "2025-02-10T13:40:51Z")
Hi guys, I get above error when running confluent local service. Any thoughts on this. Thanks in advance. --- ## [Extract kafka record key and add it to record value](https://forum.confluent.io/t/extract-kafka-record-key-and-add-it-to-record-value/36550)
**Author:** [@Metalmania97](https://forum.confluent.io/u/Metalmania97)\ **Replies:** 1\ **Last updated:** [24 January 2025 16:16 UTC](https://forum.confluent.io/t/extract-kafka-record-key-and-add-it-to-record-value/36550 "2025-01-24T16:16:33Z")
Hello. I have the following kafka record key : mqtt/temp/5 and the kafka record value : { "message\_id": "19ce932c-cc1f-4409-97f7-0e45a9a29c02", "temperature": 86.82796014582067, "timestamp": "2025-01-24T17:35:50.75… --- ## [Ksql hopping windows](https://forum.confluent.io/t/ksql-hopping-windows/13456)
**Author:** [@walt12254](https://forum.confluent.io/u/walt12254)\ **Replies:** 0\ **Last updated:** [5 December 2024 08:12 UTC](https://forum.confluent.io/t/ksql-hopping-windows/13456 "2024-12-05T08:12:33Z")
Hi all, I’m looking for some guidance on an issue I’m having with my hopping windows. I have a pipeline set up which accepts a nested json message into a stream which pushes messages into a hopping window if certain cr… --- ## [A question about event ordering](https://forum.confluent.io/t/a-question-about-event-ordering/13253)
**Author:** [@miles](https://forum.confluent.io/u/miles)\ **Replies:** 0\ **Last updated:** [17 November 2024 22:53 UTC](https://forum.confluent.io/t/a-question-about-event-ordering/13253 "2024-11-17T22:53:29Z")
Hey all, I have been using Kafka Streams for a problem I am working on and I started to think about implementing the same functionality with ksqldb to leverage the existing aggregations and functions as well as the flex… --- ## [ksqlDB Standalone version/package](https://forum.confluent.io/t/ksqldb-standalone-version-package/13130)
**Author:** [@wpirraglia](https://forum.confluent.io/u/wpirraglia)\ **Replies:** 0\ **Last updated:** [14 November 2024 14:40 UTC](https://forum.confluent.io/t/ksqldb-standalone-version-package/13130 "2024-11-14T14:40:57Z")
I notice the ksqldb.io domain now redirects to the confluent site, with the standalone deploy option gone, and mention that ksqldb is a commercial component of the confluent platform. However I’ve seen in the docker comp… --- ## [Retention Period of KSQL Table and Stream](https://forum.confluent.io/t/retention-period-of-ksql-table-and-stream/12479)
**Author:** [@ssunil9940](https://forum.confluent.io/u/ssunil9940)\ **Replies:** 0\ **Last updated:** [5 November 2024 13:35 UTC](https://forum.confluent.io/t/retention-period-of-ksql-table-and-stream/12479 "2024-11-05T13:35:48Z")
Hi guys, I’m working with the Confluent platform and experimenting with KSQL DB. I’d like to clarify the data retention periods for KSQL Tables and Streams. Here are my scenarios - If I have a source topic with a reten… --- ## [Handling Tombstone Records while Structuring primary key](https://forum.confluent.io/t/handling-tombstone-records-while-structuring-primary-key/12444)
**Author:** [@Iernst95](https://forum.confluent.io/u/Iernst95)\ **Replies:** 0\ **Last updated:** [28 October 2024 18:45 UTC](https://forum.confluent.io/t/handling-tombstone-records-while-structuring-primary-key/12444 "2024-10-28T18:45:48Z")
I’m having an issue in my ksql application where I am losing tombstone records due to my topic-backed stream being queried by tables but streams don’t have tombstone semantics, so they get dropped. The reason I need to … --- ## [Can I use ksql across multiple environments?](https://forum.confluent.io/t/can-i-use-ksql-across-multiple-environments/12417)
**Author:** [@ewhjelle](https://forum.confluent.io/u/ewhjelle)\ **Replies:** 0\ **Last updated:** [24 October 2024 14:06 UTC](https://forum.confluent.io/t/can-i-use-ksql-across-multiple-environments/12417 "2024-10-24T14:06:48Z")
I have a topic with out schema, and want to use streaming to transfer messages to another topic with schema to use a JDBC connector. Is it possible to do this across environments and clusters in confluent cloud? I want t… --- ## [KSQL Not Handling Deletions in Complex Query with Multiple Joins—Need Help Resolving Issue](https://forum.confluent.io/t/ksql-not-handling-deletions-in-complex-query-with-multiple-joins-need-help-resolving-issue/12409)
**Author:** [@shubhamcodes](https://forum.confluent.io/u/shubhamcodes)\ **Replies:** 0\ **Last updated:** [23 October 2024 12:49 UTC](https://forum.confluent.io/t/ksql-not-handling-deletions-in-complex-query-with-multiple-joins-need-help-resolving-issue/12409 "2024-10-23T12:49:09Z")
I’m encountering an issue with my Kafka Streams and KSQL setup where deletions in my source PostgreSQL database are not being reflected in one of my KSQL tables. I’m using Debezium to capture changes from a PostgreSQL d… --- ## [How I understand weather kafta broker topic is connected with backend kafta stream server correctly?](https://forum.confluent.io/t/how-i-understand-weather-kafta-broker-topic-is-connected-with-backend-kafta-stream-server-correctly/12390)
**Author:** [@Abhijeet241093](https://forum.confluent.io/u/Abhijeet241093)\ **Replies:** 0\ **Last updated:** [21 October 2024 02:58 UTC](https://forum.confluent.io/t/how-i-understand-weather-kafta-broker-topic-is-connected-with-backend-kafta-stream-server-correctly/12390 "2024-10-21T02:58:24Z")
• Hardware Platform (Jetson / GPU) \* nano • DeepStream Version 7.0 • JetPack Version (valid for Jetson only) 6.0 • TensorRT Version 8.6.2.3-1+cuda12.2 • NVIDIA GPU Driver Version (valid for GPU only) NVIDIA-SMI 540.2… --- ## [Serializer error when inserting in table with JSON\_SR](https://forum.confluent.io/t/serializer-error-when-inserting-in-table-with-json-sr/12321)
**Author:** [@mrt181](https://forum.confluent.io/u/mrt181)\ **Replies:** 2\ **Last updated:** [9 October 2024 23:23 UTC](https://forum.confluent.io/t/serializer-error-when-inserting-in-table-with-json-sr/12321 "2024-10-09T23:23:02Z")
I have this simple example json-schema: { "$schema": "https://json-schema.org/draft/2020-12/schema", "$id": "https://example.schema/test/v1", "title": "Test", "required": \[ "id", "values" \], "additio… --- ## [Period Retention of state store for table windowed](https://forum.confluent.io/t/period-retention-of-state-store-for-table-windowed/12312)
**Author:** [@rununrath](https://forum.confluent.io/u/rununrath)\ **Replies:** 0\ **Last updated:** [2 October 2024 17:24 UTC](https://forum.confluent.io/t/period-retention-of-state-store-for-table-windowed/12312 "2024-10-02T17:24:18Z")
Hi, I would like to ask about the relationship between window retention and state store of table. In case, CREATE TABLE … WINDOW TUMBLING (SIZE 10 SECONDS, RETENTION 2 DAYS) What’s the impact of RETENTION 2 DAYS ? D… --- ## [Handling Empty Events with latest\_by\_offset() in Transition Detection](https://forum.confluent.io/t/handling-empty-events-with-latest-by-offset-in-transition-detection/11384)
**Author:** [@olk](https://forum.confluent.io/u/olk)\ **Replies:** 0\ **Last updated:** [5 September 2024 18:16 UTC](https://forum.confluent.io/t/handling-empty-events-with-latest-by-offset-in-transition-detection/11384 "2024-09-05T18:16:55Z")
Hi all, I’m encountering an issue using latest\_by\_offset() where empty events are sometimes generated in my stream. Here’s the scenario: {‘key’: ‘0’, ‘x’: ‘A’} {‘key’: ‘0’, ‘x’: ‘A’} {‘key’: ‘0’, ‘x’: ‘B’} {‘key’: … --- ## [Are ksqlDB push queries distributed across cluster?](https://forum.confluent.io/t/are-ksqldb-push-queries-distributed-across-cluster/11167)
**Author:** [@DustinKLo](https://forum.confluent.io/u/DustinKLo)\ **Replies:** 2\ **Last updated:** [7 August 2024 18:37 UTC](https://forum.confluent.io/t/are-ksqldb-push-queries-distributed-across-cluster/11167 "2024-08-07T18:37:24Z")
We have a ksqlDB cluster with 5 nodes and a stream created that reads from a topic: CREATE OR REPLACE STREAM topic\_stream WITH ( KAFKA\_TOPIC='kafka\_topic', VALUE\_FORMAT='AVRO' ); We also have a push query that… --- ## [Junk in key of a table created from other streams](https://forum.confluent.io/t/junk-in-key-of-a-table-created-from-other-streams/11149)
**Author:** [@chainhead](https://forum.confluent.io/u/chainhead)\ **Replies:** 8\ **Last updated:** [1 August 2024 02:21 UTC](https://forum.confluent.io/t/junk-in-key-of-a-table-created-from-other-streams/11149 "2024-08-01T02:21:36Z")
I am creating a table with CREATE TABLE k\_events WITH (KAFKA\_TOPIC='events', KEY\_FORMAT='KAFKA', VALUE\_FORMAT='JSON') as SELECT id, AS\_VALUE(id) as message\_id, COLLECT\_LIST(output) as output from k\_merged WINDOW TUMBLING… --- ## [Group by column not seen in result](https://forum.confluent.io/t/group-by-column-not-seen-in-result/11107)
**Author:** [@chainhead](https://forum.confluent.io/u/chainhead)\ **Replies:** 1\ **Last updated:** [22 July 2024 14:36 UTC](https://forum.confluent.io/t/group-by-column-not-seen-in-result/11107 "2024-07-22T14:36:25Z")
I created this table CREATE TABLE k\_events WITH (KAFKA\_TOPIC='t\_events', KEY\_FORMAT='KAFKA', VALUE\_FORMAT='JSON') as SELECT id, COLLECT\_LIST(output) as machine\_condition from k\_merged WINDOW TUMBLING (SIZE 5 SECOND) GRO… --- ## [Type cast from integer to long?](https://forum.confluent.io/t/type-cast-from-integer-to-long/11095)
**Author:** [@chainhead](https://forum.confluent.io/u/chainhead)\ **Replies:** 1\ **Last updated:** [19 July 2024 16:24 UTC](https://forum.confluent.io/t/type-cast-from-integer-to-long/11095 "2024-07-19T16:24:42Z")
I created a stream in KSQLDB with data type as BIGINT. I am inserting some rows into this stream with hard coded values e.g., -1, 100, etc. It seems, the INSERT considers these hard coded values as INT and therefore, th… --- ## [Merge multiple streams into one](https://forum.confluent.io/t/merge-multiple-streams-into-one/11084)
**Author:** [@chainhead](https://forum.confluent.io/u/chainhead)\ **Replies:** 3\ **Last updated:** [18 July 2024 14:35 UTC](https://forum.confluent.io/t/merge-multiple-streams-into-one/11084 "2024-07-18T14:35:49Z")
Is there a KSQL way to merge i.e. concatenate multiple streams into one? For example, is there a KSQL way to achieve the same result as this tutorial? --- ## [Error when using -\>\* to query struct in pull query](https://forum.confluent.io/t/error-when-using-to-query-struct-in-pull-query/11064)
**Author:** [@nhutan](https://forum.confluent.io/u/nhutan)\ **Replies:** 3\ **Last updated:** [18 July 2024 14:01 UTC](https://forum.confluent.io/t/error-when-using-to-query-struct-in-pull-query/11064 "2024-07-18T14:01:47Z")
“@type”:“statement\_error”, “error\_code”:40001, “message”:“Cannot cast io.confluent.ksql.parser.tree.StructAll to io.confluent.ksql.parser.tree.SingleColumn” I got the above error when trying to run a pull query that i… --- ## [Unable to create stream with Schema Registry](https://forum.confluent.io/t/unable-to-create-stream-with-schema-registry/11058)
**Author:** [@chainhead](https://forum.confluent.io/u/chainhead)\ **Replies:** 4\ **Last updated:** [15 July 2024 16:54 UTC](https://forum.confluent.io/t/unable-to-create-stream-with-schema-registry/11058 "2024-07-15T16:54:39Z")
This command fails: CREATE STREAM test WITH (KAFKA\_TOPIC='test', PARTITIONS=10, VALUE\_FORMAT='JSON\_SR'); with Schema registry fetch for topic value request failed for topic: test. Whereas, in the schema registry, I can s… [Next page](https://forum.confluent.io/c/stream-processing/ksqldb/11.md?page=1)