Learn how to preview single-table data and explore data visually or with SQL in the DLF console.
Use cases
Data Preview works well when you need to:
Get a quick look at the content and distribution of a table.
Spot-check whether data meets expectations with sampled previews.
View actual field values to verify the table schema.
Run simple single-table queries without leaving the console.
Data Discovery is a better fit when you need to:
Filter and preview data through a visual interface.
Run cross-table queries and aggregate analysis with custom SQL.
Export result sets.
Both features use default compute resources and are best suited for quick exploration of small datasets. For large-scale analysis, use dedicated compute engines such as Realtime Compute for Apache Flink, EMR Serverless Spark, or EMR Serverless StarRocks.
Pricing
Data Preview and Data Exploration are currently in beta and free to use.
Prerequisites
You need SELECT permission on the target table. To grant permissions, see Manage data permissions.
Data preview
Procedure
Log on to the DLF console.
In the left-side navigation pane, choose Catalog. In the catalog tree, navigate to the target Catalog > Database > Table.
On the table details page, click the Data Preview tab.
In the Output Fields section, select the columns to return. Select Select All (\*) to include all fields, or pick specific fields to preview.
(Optional) In the Filter Conditions section, add WHERE conditions to filter the data. You can use common comparison operators and logical combinations. If no filter is set, all data is returned.
(Optional) In the Query Enhancement section, configure advanced options:
Group By: Aggregate results by one or more fields.
Order By: Sort results by one or more fields.
Limit: Set a maximum number of rows to return.
Click Execute Query to run the query. To start over, click Reset.
Queries on large tables may time out due to default compute resource limits. Use Limit and filter conditions to narrow the result set.
Data discovery
Procedure
Log on to the DLF console.
In the left-side navigation pane, choose Data Discovery.
Choose an exploration mode:
Visual Query: Filter and preview data visually without writing SQL. The system generates SQL automatically based on your selections.
SQL Query: Write and run SQL queries directly. Includes syntax highlighting, validation, and result set export.
You can switch between modes at any time from the top of the page.
Visual query
In the query configuration area, select a Catalog, Database, and Table.
In the Output Fields section, select the columns to return. Select Select All (\*) to include all fields, or pick specific fields.
(Optional) In the Filter Conditions section, add WHERE conditions to filter the data.
(Optional) In the Query Enhancement section, configure advanced options:
Group By: Aggregate results by one or more fields.
Order By: Sort results by one or more fields.
Limit: Set a maximum number of rows to return.
Click Execute Query to run the query. To start over, click Reset.
SQL query
In the catalog tree on the left, select the target Catalog and Database, then click New Query to open a query editor tab. The editor provides syntax highlighting and validation.
Example:
SELECT col1, col2, COUNT(*) AS cnt FROM my_table WHERE dt = '2024-01-01' GROUP BY col1, col2 ORDER BY cnt DESC LIMIT 100;Click Run to view results.
(Optional) Review past queries in the query list and export result sets as needed.