> ## Documentation Index > Fetch the complete documentation index at: https://docs.fly.io/llms.txt > Use this file to discover all available pages before exploring further. # Query Database > Run read-only SQL against a database and return the final result set. The SQL runs as pg_read_all_data inside a read-only transaction with a statement timeout, so it can read every table but cannot change data or schema. Results over 1000 rows are rejected rather than truncated; add a LIMIT. System databases cannot be queried. Requires only read access to the organization. ## OpenAPI ````yaml /api/machines/openapi.json post /v1/postgres/{postgres_cluster_id}/databases/{database_name}/query openapi: 3.1.0 info: title: Machines API description: >- This site hosts documentation generated from the Fly.io Machines API OpenAPI specification. Visit our complete [Machines API docs](https://fly.io/docs/machines/api/) for how to get started, more information about each endpoint, parameter descriptions, and examples. contact: {} license: name: Apache 2.0 url: http://www.apache.org/licenses/LICENSE-2.0.html version: '1.0' servers: - url: https://api.machines.dev security: - FlyBearerAuth: [] tags: - name: Apps description: >- This site hosts documentation generated from the Fly.io Machines API OpenAPI specification. Visit our complete [Machines API docs](https://fly.io/docs/machines/api/apps-resource/) for details about using the Apps resource. - name: Machines description: >- This site hosts documentation generated from the Fly.io Machines API OpenAPI specification. Visit our complete [Machines API docs](https://fly.io/docs/machines/api/machines-resource/) for details about using the Machines resource. - name: TLS Certificates description: > This site hosts documentation generated from the Fly.io Machines API OpenAPI specification. Visit our complete [Machines API docs](https://fly.io/docs/machines/api/certificates-resource/) for details about using the TLS Certificates resource. - name: Volumes description: >- This site hosts documentation generated from the Fly.io Machines API OpenAPI specification. Visit our complete [Machines API docs](https://fly.io/docs/machines/api/volumes-resource/) for details about using the Volumes resource. - name: Postgres Clusters description: >- Create and manage Postgres clusters, including databases, users, extensions, backups, and app attachments. externalDocs: url: https://fly.io/docs/machines/working-with-machines/ paths: /v1/postgres/{postgres_cluster_id}/databases/{database_name}/query: post: tags: - Postgres Clusters summary: Query Database description: >- Run read-only SQL against a database and return the final result set. The SQL runs as pg_read_all_data inside a read-only transaction with a statement timeout, so it can read every table but cannot change data or schema. Results over 1000 rows are rejected rather than truncated; add a LIMIT. System databases cannot be queried. Requires only read access to the organization. operationId: Postgres_databases_query parameters: - name: postgres_cluster_id in: path description: Managed Postgres Cluster ID required: true schema: type: string - name: database_name in: path description: Database Name required: true schema: type: string requestBody: description: Query content: application/json: schema: $ref: '#/components/schemas/queryPostgresDatabaseRequest' required: true responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/postgresQueryResponse' '400': description: sql is missing, not a string, or too long content: application/json: schema: $ref: '#/components/schemas/PostgresErrorResponse' '401': description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/PostgresErrorResponse' '404': description: >- 'Cluster not found' for the cluster; 'Database not found' for the database content: application/json: schema: $ref: '#/components/schemas/PostgresErrorResponse' '422': description: >- The query ran and failed; status is one of invalid_request, permission_denied, read_only_violation, statement_timeout, row_limit_exceeded, execution_failed content: application/json: schema: $ref: '#/components/schemas/PostgresErrorResponse' '500': description: Unable to run the query content: application/json: schema: $ref: '#/components/schemas/PostgresErrorResponse' '503': description: >- pg-admin is unavailable; retry after the interval given by the Retry-After header content: application/json: schema: $ref: '#/components/schemas/PostgresErrorResponse' components: schemas: queryPostgresDatabaseRequest: required: - sql type: object properties: sql: type: string description: >- SQL to run, up to 102400 bytes. Multiple statements are allowed; only the last result set is returned. example: SELECT id, email FROM users LIMIT 10 postgresQueryResponse: type: object properties: columns: type: array description: Columns of the final result set, in order. items: $ref: '#/components/schemas/PostgresQueryColumn' row_count: type: integer description: Number of rows returned. rows: type: array description: >- Rows of the final result set; each row holds one JSON value per column, with NULL as null and json/jsonb as decoded JSON. items: type: array items: type: object PostgresErrorResponse: type: object properties: error: type: string description: Human-readable error message. status: type: string description: Optional machine-readable error status. example: sessions_not_terminated PostgresQueryColumn: type: object properties: name: type: string description: Column name as returned by Postgres. type: type: string description: Postgres type name. example: int8 securitySchemes: FlyBearerAuth: type: http scheme: bearer description: >- A Fly API token with access to the requested organization or resource. Send it as `Authorization: Bearer `. ````