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Operators

ksqlDB supports the following operators in value expressions.

The explanation for each operator includes a supporting example based on the following table:

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CREATE TABLE USERS (
    USERID BIGINT PRIMARY KEY,
    FIRST_NAME STRING,
    LAST_NAME STRING,
    NICKNAMES ARRAY<STRING>,
    ADDRESS STRUCT<STREET_NAME STRING, HOUSE_NUM INTEGER>
) WITH (KAFKA_TOPIC='users', VALUE_FORMAT='AVRO');

Arithmetic

The usual arithmetic operators (+,-,/,*,%) may be applied to numeric types, like INT, BIGINT, and DOUBLE:

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SELECT USERID, LEN(FIRST_NAME) + LEN(LAST_NAME) AS NAME_LENGTH FROM USERS EMIT CHANGES;

Concatenation

The concatenation operator (+,||) can be used to concatenate STRING values.

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SELECT USERID, FIRST_NAME + LAST_NAME AS FULL_NAME FROM USERS EMIT CHANGES;

You can use the + operator for multi-part concatenation, for example:

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SELECT USERID,
    TIMESTAMPTOSTRING(ROWTIME, 'yyyy-MM-dd HH:mm:ss') +
        ': :heavy_exclamation_mark: On ' +
        HOST +
        ' there were ' +
        CAST(INVALID_LOGIN_COUNT AS VARCHAR) +
        ' attempts in the last minute (threshold is >=4)'
  FROM INVALID_USERS_LOGINS_PER_HOST
  WHERE INVALID_LOGIN_COUNT>=4
  EMIT CHANGES;

Source Dereference

The source dereference operator (.) can be used to specify columns by dereferencing the source stream or table.

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SELECT USERID, USERS.FIRST_NAME FROM USERS EMIT CHANGES;

Subscript

The subscript operator ([subscript_expr]) is used to reference the value at an array index or a map key.

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SELECT USERID, NICKNAMES[1] FROM USERS EMIT CHANGES;

STRUCT dereference

Access nested data by declaring a STRUCT and using the dereference operator (->) to access its fields:

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SELECT USERID, ADDRESS->STREET, ADDRESS->HOUSE_NUM FROM USERS EMIT CHANGES;

Combine -> with . when using aliases:

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SELECT USERID, USERS.ADDRESS->STREET, U.ADDRESS->STREET FROM USERS U EMIT CHANGES;

For more information on nested data, see STRUCT.

Last update: 2020-08-05