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Json Agg

Definition​

The jsonAgg method allows you to add the JSON_AGG function to the query. The JSON_AGG is a function that accepts a set of values and returns a JSON array in which each value in the set is assigned to an element of the JSON array.

There are 2 ways to call this method:

1. Calling from a KColumn or a KTableColumn​

The only one method available to use this functionality calling from a KColumn or a KTableColumn is:

  • jsonAgg(): It does not receive any parameters. The KColumn or KTableColumn that invokes the method will be the one supplied to the JSON_AGG function.

Example​

Java code:

k
.select(
    APP_USER.EMAIL.jsonAgg(),
    APP_USER.CREATED_AT.cast(date())
)
.from(APP_USER)
.groupBy(APP_USER.CREATED_AT.cast(date()))
.multiple();

SQL generated:

SELECT
    JSON_AGG(au.email),
    CAST(au.created_at AS DATE)
FROM app_user au
GROUP BY CAST(au.created_at AS DATE)

Parameters:

  • None

2. Calling from the KFunction class​

The only one method available to use this functionality calling from the KFunction class is:

  • jsonAgg(KColumn kColumn): Receives a KColumn or a KTableColumn which will be supplied to the JSON_AGG function.

To use this way, you need to import the static functions as follows:

import static com.myzlab.k.KFunction.*;

Example​

Java code:

k
.select(
    jsonAgg(APP_USER.EMAIL),
    APP_USER.CREATED_AT.cast(date())
)
.from(APP_USER)
.groupBy(APP_USER.CREATED_AT.cast(date()))
.multiple();

SQL generated:

SELECT
    JSON_AGG(au.email),
    CAST(au.created_at AS DATE)
FROM app_user au
GROUP BY CAST(au.created_at AS DATE)

Parameters:

  • None

Support for the ORDER BY clause​

The JSON_AGG function supports being used with an ORDER BY clause.

Available methods​

  • orderBy(KColumnAllowedToOrderBy... kColumnsAllowedToOrderBy): Receives a variable quantity of columns that will be added to the ORDER BY clause. Among the possible values are: KTableColumn, KColumn, KRaw.

This method is only available after calling the jsonAgg method and is completely optional.

Example​

Java code:

k
.select(
    jsonAgg(
        concat(APP_USER.FIRST_NAME, val(" "), APP_USER.LAST_NAME)
    ).orderBy(APP_USER.FIRST_NAME.asc(), APP_USER.LAST_NAME.desc())
    APP_USER.CREATED_AT.cast(date())
)
.from(APP_USER)
.groupBy(APP_USER.CREATED_AT.cast(date()))
.multiple();

SQL generated:

SELECT
    JSON_AGG(
        CONCAT(au.first_name || ?1 || au.last_name
    ) ORDER BY au.first_name ASC, au.last_name DESC),
    CAST(au.created_at AS DATE)
FROM app_user au
GROUP BY CAST(au.created_at AS DATE)

Parameters:

  • ?1: " "