Data model in Yandex DataLens

Data in a dataset is represented as fields.

Data sourceData source

One or more tables are used as the data source.

If there are multiple tables in the source, you can join them with a JOIN operator.
When the tables are joined, a link is created between them. When you create a link, you specify the fields from the source table and merged table.

Tables are linked automatically by the first match in the field name and field data type.

In this case, you can:

• Edit fields in the link.
• Add new links or delete existing links.
• Change the type of the JOIN operator in the link (INNER, LEFT, RIGHT, or FULL).
• Manage link optimization.

JOIN is used if a query made from a chart uses fields from two or more dataset tables.

JOIN is not used if:

• The dataset contains one table.
• The dataset contains multiple tables; however, the query uses fields from only one of those tables (with link optimization enabled).

To manage the link behavior when joining data from multiple tables, use the Optimize link option in the link settings. This option is enabled by default for all links in the dataset: the JOIN operator applies if the query uses fields from two or more linked tables. You can disable the option for each individual link to make the link required. In which case the JOIN operation will be performed even if you select fields from a single table.

For more information about optimization when using JOIN, see Optimizing data when joining tables.

Data fieldsData fields

The fields define the structure and format of the dataset. The following types of fields are available:

• Dimension. Contains values that define data parameters, such as a city, date of purchase, or product category. The aggregation function is not applied to fields with a dimension; otherwise, the field becomes a measure. In the interface, dimensions are displayed in green.
• Measure. Contains numeric values the aggregation functions (information) apply to, such as the amount of clicks and the number of click-throughs. If you remove the aggregation function from this field, it will become a dimension. In the interface, measures are displayed in blue.

In the dataset creation interface and wizard, you can duplicate fields, create fields, and use aggregation functions.

DataLens allows you to create calculable fields using formulas. To write formulas, you can use existing dataset fields, constants, and functions. For a full list of functions, see the Function reference.

For more information about calculable fields, see Calculated fields in Yandex DataLens.

Aggregating dataAggregating data

The following aggregation functions are available for fields with different data types:

Function	Description	Supported types
No	Without aggregation	All types
Average	Arithmetic mean value	Fractional number Integer
Quantity	Number of records	String Date Date and time Fractional number Integer
Number of unique	Number of unique records	String Date Date and time Fractional number Integer
Maximum	Maximum value	Date Date and time Fractional number Integer
Minimum	Minimum value	Date Date and time Fractional number Integer
Amount	Sum of values	Fractional number Integer

Additional aggregation functions are available in calculated fields.

To learn more about data types, see Yandex DataLens data types.

Useful linksUseful links

• Working with a dataset in Yandex DataLens