# Presto 316 Documentation

## 9.16. DESCRIBE OUTPUT

## Synopsis

    DESCRIBE OUTPUT statement_name

## Description

List the output columns of a prepared statement, including the column name (or alias), catalog, schema, table, type, type size in bytes, and a boolean indicating if the column is aliased.

## Examples

Prepare and describe a query with four output columns:

    PREPARE my_select1 FROM
    SELECT * FROM nation

    DESCRIBE OUTPUT my_select1;

     Column Name | Catalog | Schema | Table  |  Type   | Type Size | Aliased
    -------------+---------+--------+--------+---------+-----------+---------
     nationkey   | tpch    | sf1    | nation | bigint  |         8 | false
     name        | tpch    | sf1    | nation | varchar |         0 | false
     regionkey   | tpch    | sf1    | nation | bigint  |         8 | false
     comment     | tpch    | sf1    | nation | varchar |         0 | false
    (4 rows)

Prepare and describe a query whose output columns are expressions:

    PREPARE my_select2 FROM
    SELECT count(*) as my_count, 1+2 FROM nation

    DESCRIBE OUTPUT my_select2;

     Column Name | Catalog | Schema | Table |  Type  | Type Size | Aliased
    -------------+---------+--------+-------+--------+-----------+---------
     my_count    |         |        |       | bigint |         8 | true
     _col1       |         |        |       | bigint |         8 | false
    (2 rows)

Prepare and describe a row count query:

    PREPARE my_create FROM
    CREATE TABLE foo AS SELECT * FROM nation

    DESCRIBE OUTPUT my_create;

     Column Name | Catalog | Schema | Table |  Type  | Type Size | Aliased
    -------------+---------+--------+-------+--------+-----------+---------
     rows        |         |        |       | bigint |         8 | false
    (1 row)

## See Also

PREPARE