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Time operations

Time units

The following list shows valid time units for the SIZE, ADVANCE BY, SESSION, and WITHIN clauses, or to pass as time unit parameters in functions.

  • DAY, DAYS
  • HOUR, HOURS
  • MINUTE, MINUTES
  • SECOND, SECONDS
  • MILLISECOND, MILLISECONDS

For more information, see Windows in SQL Queries.

Timestamp formats

Important

This section refers to timestamps as a field in records. For information on the TIMESTAMP data type, see Timestamp types.

Time-based operations, like windowing, process records according to the timestamp in ROWTIME. By default, the implicit ROWTIME pseudo column is the timestamp of a message in a Kafka topic. Timestamps have an accuracy of one millisecond.

Use the TIMESTAMP property to override ROWTIME with the contents of the specified column. Define the format of a record's timestamp by using the TIMESTAMP_FORMAT property.

If you use the TIMESTAMP property but don't set TIMESTAMP_FORMAT, ksqlDB assumes that the timestamp field is a bigint. If you set TIMESTAMP_FORMAT, the TIMESTAMP field must be of type varchar and have a format that the DateTimeFormatter Java class can parse.

If your timestamp format has embedded single quotes, you can escape them by using two successive single quotes, ''. For example, to escape 'T', write ''T''. The following examples show how to escape the ' character in SQL statements.

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-- Example timestamp format: yyyy-MM-dd'T'HH:mm:ssX
CREATE STREAM TEST (id BIGINT KEY, event_timestamp VARCHAR)
  WITH (
    kafka_topic='test_topic',
    value_format='JSON',
    timestamp='event_timestamp',
    timestamp_format='yyyy-MM-dd''T''HH:mm:ssX'
  );

-- Example timestamp format: yyyy.MM.dd G 'at' HH:mm:ss z
CREATE STREAM TEST (id BIGINT KEY, event_timestamp VARCHAR)
  WITH (
    kafka_topic='test_topic',
    value_format='JSON',
    timestamp='event_timestamp',
    timestamp_format='yyyy.MM.dd G ''at'' HH:mm:ss z'
  );

-- Example timestamp format: hh 'o'clock' a, zzzz
CREATE STREAM TEST (id BIGINT KEY, event_timestamp VARCHAR)
  WITH (
    kafka_topic='test_topic',
    value_format='JSON',
    timestamp='event_timestamp',
    timestamp_format='hh ''o''clock'' a, zzzz'
  );

For more information on timestamp formats, see DateTimeFormatter.

Last update: 2021-03-12