> ## Documentation Index
> Fetch the complete documentation index at: https://docs.validio.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Data Sampling

> Preview a tabulated sample of rows from your source to inspect actual data values and verify data patterns.

Data sampling in Validio displays a tabulated preview of rows from your source or catalog asset, letting you inspect actual data values and verify data patterns. You can also use [Data Profiling](https://docs.validio.io/v10.3/docs/schema-and-profiling/data-profiling.md) to generate statistical analysis of your fields.

Sampling returns real rows from your data rather than computed metrics, so the preview is transient: it is held in memory for display only — never written to Validio storage and discarded when you close or reload it. A sample returns at most **1,000 rows** (the configurable **Row limit** cannot exceed this hard cap). For more on what Validio stores versus what stays in your warehouse — including the other features that display raw rows transiently — see [Data Handling and Retention](https://docs.validio.io/v10.3/docs/deployment/data-handling-and-retention.md).

![The data sampling configuration dialog and the resulting preview of rows](https://mintcdn.com/validio/36lh-6_uXUsulPvT/images/docs/schema-and-profiling/800-datasampling-config.png?fit=max\&auto=format\&n=36lh-6_uXUsulPvT\&q=85\&s=3a77d18f1953085a7bb0fbccf50ab8f0)

Data sampling configuration and preview

## Running a sample

To sample data from your source or catalog asset:

1. Navigate to the **[Schema & Profiling](https://docs.validio.io/v10.3/docs/schema-and-profiling.md)** tab.

2. Click **Sample data** and configure the sample size and fields in the dialog:

   * **Sampling Percentage**: (Only available for tables and materialized views.) Use the slider or enter a number to adjust the percentage of data to include in the sample. Lower values speed up sampling on large tables. Defaults to 10%.

   * **Data Scope**: (Recommended) Cap the execution time on large datasets by limiting the fields and number of rows sampled:

     | Setting | Description |
     | :- | :- |
     | Fields | Select specific fields to include in the sample. By default, all fields are included. |
     | Row limit | Set the maximum number of rows to include in the sample. Defaults to 50 rows, up to a maximum of 1,000. |

   * **Lookback Filter**: (Recommended) Limit the data volume scanned by targeting only a specific window of recent data:

     | Setting | Description |
     | :- | :- |
     | Lookback field | Select a timestamp or date field to define the sampling window. This limits the sample to recent data rather than scanning the full dataset. |
     | Lookback duration | The specific amount of time to look back when filtering data. Use this with the **Lookback field** to sample only recent data. |

   * **Credential** (Only for catalog assets): Select a credential to use for displaying sample data.

   The dialog also includes a **SQL query** that is auto-generated from your settings. You can edit this query directly for more control, but note that manual edits are not synced back to the settings above. Click **Reset query** to discard any manual edits and regenerate the query from the current settings.

3. Click **Load samples** to display the results.
   * To cancel a sampling run (for example, if sampling takes too long to complete), click **Cancel** and adjust the settings.

## Use cases

Data Sampling is useful for:

* Spot-checking that actual values match the detected schema and data types.
* Verifying data patterns before configuring validators.
* Investigating unexpected values or formats flagged during profiling or validation.