# Using Relationship Queries with Data Category Selection Objects

Data categories are used to classify records. In SOQL, you can use the *Article*\__DataCategorySelection or QuestionDataCategorySelection objects. You can also build a relationship query with the `DataCategorySelections` relationship name in a `FROM` clause.

Imagine an `Offer` article type. The following query returns the ID of any categorization associated with an offer and the ID of the categorized article.

```soql
SELECT Id,ParentId
FROM Offer__DataCategorySelection

```

The following example uses the `DataCategorySelections` relationship name to build a relationship query that returns the ID of published offers and the ID of all the categorizations associated to these offers.

```soql
SELECT Id, Title,
  (
    SELECT Id
    FROM DataCategorySelections
  )
FROM Offer__kav WHERE PublishStatus='online'
```