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> Documentation for Describe Table

# DESCRIBE TABLE

Returns information about table columns.

**Syntax**

```sql theme={null}
DESC|DESCRIBE TABLE [db.]table [INTO OUTFILE filename] [FORMAT format]
```

The `DESCRIBE` statement returns a row for each table column with the following [String](/reference/data-types/string) values:

* `name` — A column name.
* `type` — A column type.
* `default_type` — A clause that is used in the column [default expression](/reference/statements/create/table): `DEFAULT`, `MATERIALIZED` or `ALIAS`. If there is no default expression, then empty string is returned.
* `default_expression` — An expression specified after the `DEFAULT` clause.
* `comment` — A [column comment](/reference/statements/alter/column#comment-column).
* `codec_expression` — A [codec](/reference/statements/create/table#column_compression_codec) that is applied to the column.
* `ttl_expression` — A [TTL](/reference/engines/table-engines/mergetree-family/mergetree#table_engine-mergetree-ttl) expression.
* `is_subcolumn` — A flag that equals `1` for internal subcolumns. It is included into the result only if subcolumn description is enabled by the [describe\_include\_subcolumns](/reference/settings/session-settings#describe_include_subcolumns) setting.

All columns in [Nested](/reference/data-types/nested-data-structures) data structures are described separately. The name of each column is prefixed with a parent column name and a dot.

To show internal subcolumns of other data types, use the [describe\_include\_subcolumns](/reference/settings/session-settings#describe_include_subcolumns) setting.

**Example**

```sql title="Query" theme={null}
CREATE TABLE describe_example (
    id UInt64, text String DEFAULT 'unknown' CODEC(ZSTD),
    user Tuple (name String, age UInt8)
) ENGINE = MergeTree() ORDER BY id;

DESCRIBE TABLE describe_example;
DESCRIBE TABLE describe_example SETTINGS describe_include_subcolumns=1;
```

```text title="Response" theme={null}
┌─name─┬─type──────────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┐
│ id   │ UInt64                        │              │                    │         │                  │                │
│ text │ String                        │ DEFAULT      │ 'unknown'          │         │ ZSTD(1)          │                │
│ user │ Tuple(name String, age UInt8) │              │                    │         │                  │                │
└──────┴───────────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┘
```

The second query additionally shows subcolumns:

```text title="Response" theme={null}
┌─name──────┬─type──────────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┬─is_subcolumn─┐
│ id        │ UInt64                        │              │                    │         │                  │                │            0 │
│ text      │ String                        │ DEFAULT      │ 'unknown'          │         │ ZSTD(1)          │                │            0 │
│ user      │ Tuple(name String, age UInt8) │              │                    │         │                  │                │            0 │
│ user.name │ String                        │              │                    │         │                  │                │            1 │
│ user.age  │ UInt8                         │              │                    │         │                  │                │            1 │
└───────────┴───────────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┴──────────────┘
```

The DESCRIBE statement can also be used with subqueries or scalar expressions:

```SQL theme={null}
DESCRIBE SELECT 1 FORMAT TSV;
```

or

```SQL theme={null}
DESCRIBE (SELECT 1) FORMAT TSV;
```

```text title="Response" theme={null}
1       UInt8
```

This usage returns metadata about the result columns of the specified query or subquery. It is useful for understanding the structure of complex queries before execution.

**See Also**

* [describe\_include\_subcolumns](/reference/settings/session-settings#describe_include_subcolumns) setting.