# Query metadata from a database

You can use the **Query metadata from a database** step to retrieve metadata from six different JDBC metadata discovery types. This is most useful with metadata injection.

| JDBC Metadata Discovery Types | Description                                                                                                                        |
| ----------------------------- | ---------------------------------------------------------------------------------------------------------------------------------- |
| Catalog                       | Gets a list of catalogs from the database servers. For databases that do not support catalogs, this step type will output no rows. |
| Schemas                       | Gets a list of schemas from the database servers. For databases that do not support schemas, this step type will output no rows.   |
| Tables                        | Gets a list of tables from the database.                                                                                           |
| Columns                       | Gets a list of columns from the database.                                                                                          |
| Primary keys                  | Gets a list of primary keys from the database.                                                                                     |
| Foreign keys                  | Gets a list of foreign keys from the database.                                                                                     |

**Note:** This step makes use of the standard JDBC API to collect metadata. Some database JDBC drivers do not fully implement the JDBC API. For databases that do not fully implement the JDBC API, it is possible that these steps may return unexpected results including no data or partial results. If this occurs, include a **%** in additional fields and/or upgrade the installed JDBC driver. If upgrading the driver does not resolve the issue, you may have to contact your database vendor.


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# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.pentaho.com/pdia-data-integration/10.2-data-integration/pdi-transformation-steps-reference-overview/query-metadata-from-a-database-article.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.