---
title: "DESCRIBE"
slug: "dev-database-reference-sql-describe"
updated: 2026-10-30T18:19:11Z
published: 2026-10-30T18:19:11Z
canonical: "docs.vastdata.com/dev-database-reference-sql-describe"
---

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

# DESCRIBE

*Applies to VAST Cluster 5.5.*

Shows a table's columns and their types.

## Syntax

```
DESCRIBE [TABLE] "<bucket>/<schema>".<table>
SHOW "<bucket>/<schema>".<table>
```

## Parameters and rules

`DESCRIBE`, `DESCRIBE TABLE` and `SHOW` return the same result: one row per column, with six columns:

| Result column | Holds |
| --- | --- |
| `column_name` | The column's name |
| `column_type` | Its SQL type, for example `BIGINT`, `VARCHAR`, `STRUCT(lat DOUBLE)` or `TIMESTAMP WITH TIME ZONE` |
| `null`, `key`, `default`, `extra` | In the captures, `null` was always `YES` and the others empty: the Query Engine has no `NOT NULL`, keys or defaults. |

What `DESCRIBE` doesn't show:

- **The sort key** of a sorted table. Use the Python SDK's table metadata ([data modeling](/develop/docs/dev-database-guides-data-modeling#sorted-tables)).
- **The vector index** settings (metric and quantization). The vector column shows as `VECTOR(FLOAT, &lt;dim&gt;)`; see [vector search SQL](/develop/docs/dev-database-reference-sql-vector-search).
- **Whether a column can be read** through the Query Engine. `MAP` and `TIMESTAMP WITH TIME ZONE` columns are listed, but selecting them fails; see [data types in SQL](/develop/docs/dev-database-reference-sql-data-types).

`DESCRIBE` of a query, such as `DESCRIBE (SELECT rowid FROM ...)`, fails with an internal error message. Use `typeof()` instead: `SELECT typeof(rowid) FROM &lt;table&gt; LIMIT 1`.

If a row filter or column mask applies to you on the table, `DESCRIBE` fails like any other statement on it ([vector search security](/develop/docs/dev-vector-search-operations-security#which-rules-work-with-vector-search)). With a column deny rule, `DESCRIBE` lists only the columns you may read.

## What happens on the cluster

`DESCRIBE` reads the table's definition from the database's catalog. It reads no rows.

## Example

The examples use the `run()` helper and the environment variables described in the [SQL reference](/develop/docs/dev-database-reference-sql-index#example-connect-and-use-a-transaction). This block connects, and creates the schema `docs_sql_describe` with a sorted table:

```
import os
import re

import adbc_driver_manager
import adbc_driver_manager.dbapi as dbapi
import adbc_driver_vastdb

BUCKET = os.environ["VASTDB_BUCKET"]
SCHEMA = f'"{BUCKET}/docs_sql_describe"'

def connect(autocommit=True):
    return dbapi.connect(
        driver=adbc_driver_vastdb.get_driver_path(),
        db_kwargs={
            "vast.db.endpoint": os.environ["QE_ENDPOINT"],
            "vast.db.access_key": os.environ["AWS_ACCESS_KEY_ID"],
            "vast.db.secret_key": os.environ["AWS_SECRET_ACCESS_KEY"],
        },
        autocommit=autocommit,
    )

def server_message(e):
    """The server's message in a driver error, without the request ID or the echoed statement."""
    text = re.sub(r"\[req=0x[0-9a-f]+\]: ", "", str(e))
    found = (re.search(r'message: "(.*?)", request_id', text, re.S)
             or re.search(r"description: (.*)\)", text, re.S))
    message = found.group(1) if found else text.strip().splitlines()[-1]
    message = re.sub(r"^Plan query: '.*?' failed with: ", "", message, flags=re.S)
    message = re.split(r"\\n|\n", message)[0].replace('\\"', '"')
    return message.replace(BUCKET, "<bucket>")

def run(sql):
    """Run one statement. Print the rows it returns, or the error."""
    try:
        with conn.cursor() as cur:
            cur.execute(sql)
            rows = cur.fetchall() if cur.description else []
    except (adbc_driver_manager.Error, OSError) as e:
        print(f"{type(e).__name__}: {server_message(e)}")
    else:
        print(rows)

conn = connect()
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {SCHEMA}.readings "
    "(id BIGINT, city VARCHAR, taken_at TIMESTAMP, location STRUCT(lat DOUBLE, lon DOUBLE), "
    "CONSTRAINT readings_sk SORT KEY (id))")
```

```
[]
[]
```

The three forms return the same rows. The sort key isn't listed:

```
run(f"DESCRIBE {SCHEMA}.readings")
run(f"DESCRIBE TABLE {SCHEMA}.readings")
run(f"SHOW {SCHEMA}.readings")
```

```
[('id', 'BIGINT', 'YES', None, None, None), ('city', 'VARCHAR', 'YES', None, None, None), ('taken_at', 'TIMESTAMP', 'YES', None, None, None), ('location', 'STRUCT(lat DOUBLE, lon DOUBLE)', 'YES', None, None, None)]
[('id', 'BIGINT', 'YES', None, None, None), ('city', 'VARCHAR', 'YES', None, None, None), ('taken_at', 'TIMESTAMP', 'YES', None, None, None), ('location', 'STRUCT(lat DOUBLE, lon DOUBLE)', 'YES', None, None, None)]
[('id', 'BIGINT', 'YES', None, None, None), ('city', 'VARCHAR', 'YES', None, None, None), ('taken_at', 'TIMESTAMP', 'YES', None, None, None), ('location', 'STRUCT(lat DOUBLE, lon DOUBLE)', 'YES', None, None, None)]
```

To see the type of an expression, use `typeof()`:

```
run(f"INSERT INTO {SCHEMA}.readings VALUES (1, 'Lisbon', TIMESTAMP '2026-01-01 10:00:00', {{'lat': 38.7, 'lon': -9.1}})")
run(f"SELECT typeof(rowid), typeof(location.lat) FROM {SCHEMA}.readings LIMIT 1")
```

```
[(1,)]
[('DECIMAL(38,0)', 'DOUBLE')]
```

Clean up:

```
run(f"DROP TABLE IF EXISTS {SCHEMA}.readings")
run(f"DROP SCHEMA IF EXISTS {SCHEMA}")
conn.close()
```

```
[]
[]
```

## Errors

| You wrote | Message |
| --- | --- |
| `DESCRIBE (SELECT ...)` | An internal error message that doesn't say what's wrong. Use `typeof()`. |

## Trino and Spark

Trino and Spark have their own `DESCRIBE`, and Trino's `SHOW CREATE TABLE` also shows the sort columns; see [Trino](/develop/docs/dev-database-integrations-trino#sorted-tables) and [Spark](/develop/docs/dev-database-integrations-spark#spark-sql-and-dataframes).

See also: [SHOW](/develop/docs/dev-database-reference-sql-show), [data types in SQL](/develop/docs/dev-database-reference-sql-data-types).