LIMIT Clause in Confluent Cloud for Apache Flink

Confluent Cloud for Apache Flink® enables constraining the number of rows returned by a SELECT statement.

Description

The LIMIT clause constrains the number of rows returned by a SELECT statement.

Usually, this clause is used in conjunction with ORDER BY to ensure that the results are deterministic.

Example

In the Flink SQL shell or in a Cloud Console workspace, run the following commands to see an example of the LIMIT clause. The following example selects the first 3 rows from a web page clicks table.

  1. Create a table for web page click events.

    -- Create a table for web page click events.
CREATE TABLE clicks (
  ip_address VARCHAR,
  url VARCHAR,
  click_ts_raw BIGINT
);

  2. Populate the table with mock clickstream data.

    -- Populate the table with mock clickstream data.
INSERT INTO clicks
VALUES( '10.0.0.1',  'https://acme.com/index.html',     1692812175),
      ( '10.0.0.12', 'https://apache.org/index.html',   1692826575),
      ( '10.0.0.13', 'https://confluent.io/index.html', 1692826575),
      ( '10.0.0.1',  'https://acme.com/index.html',     1692812175),
      ( '10.0.0.12', 'https://apache.org/index.html',   1692819375),
      ( '10.0.0.13', 'https://confluent.io/index.html', 1692826575);

    Press ENTER to return to the SQL shell. Because INSERT INTO VALUES is a point-in-time statement, it exits after it completes inserting records.

  3. View the rows in the clicks table and limit the result to 3 rows.

    SELECT * FROM clicks LIMIT 3;

    Your output should resemble:

    ip_address url                             click_ts_raw
10.0.0.1   https://acme.com/index.html     1692812175
10.0.0.12  https://apache.org/index.html   1692826575
10.0.0.13  https://confluent.io/index.html 1692826575

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