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Count Distinct

Definition​

The countDistinct method allows you to add the COUNT(DISTINCT expression) function to the query. The COUNT(DISTINCT expression) function returns the number of rows returned by a SELECT statement. However, it does not consider NULL values in the expression and does not consider repeated values.

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:

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

Example​

Java code:

k
.select(APP_USER.ID.countDistinct())
.from(APP_USER)
.multiple();

SQL generated:

SELECT COUNT(DISTINCT au.id)
FROM app_user au

Parameters:

  • None

2. Calling from the KFunction class​

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

  • countDistinct(KColumn kColumn): Receives a KColumn or a KTableColumn which will be supplied to the COUNT 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(countDistinct(APP_USER.ID))
.from(APP_USER)
.multiple();

SQL generated:

SELECT COUNT(DISTINCT au.id)
FROM app_user au

Parameters:

  • None