Describe

Describing a Table

To view the schema of a table, use the DESCRIBE statement (or its aliases DESC and SHOW) followed by the table name.

CREATE TABLE tbl (i INTEGER PRIMARY KEY, j VARCHAR);
DESCRIBE tbl;
SHOW tbl; -- equivalent to DESCRIBE tbl;

column_name	column_type	null	key	default	extra
i	INTEGER	NO	PRI	NULL	NULL
j	VARCHAR	YES	NULL	NULL	NULL

Describing a Query

To view the schema of the result of a query, prepend DESCRIBE to a query.

DESCRIBE SELECT * FROM tbl;

column_name	column_type	null	key	default	extra
i	INTEGER	YES	NULL	NULL	NULL
j	VARCHAR	YES	NULL	NULL	NULL

Note that there are subtle differences: compared to the result when describing a table, nullability (null) and key information (key) are lost.

Using DESCRIBE in a Subquery

DESCRIBE can be used as a subquery. This allows creating a table from the description, for example:

CREATE TABLE tbl_description AS SELECT * FROM (DESCRIBE tbl);

Describing Remote Tables

It is possible to describe remote tables via the httpfs extension using the DESCRIBE TABLE statement. For example:

DESCRIBE TABLE 'https://${uri}/Star_Trek-Season_1.csv';

column_name	column_type	null	key	default	extra
season_num	BIGINT	YES	NULL	NULL	NULL
episode_num	BIGINT	YES	NULL	NULL	NULL
aired_date	DATE	YES	NULL	NULL	NULL
cnt_kirk_hookups	BIGINT	YES	NULL	NULL	NULL
cnt_downed_redshirts	BIGINT	YES	NULL	NULL	NULL
bool_aliens_almost_took_over_planet	BIGINT	YES	NULL	NULL	NULL
bool_aliens_almost_took_over_enterprise	BIGINT	YES	NULL	NULL	NULL
cnt_vulcan_nerve_pinch	BIGINT	YES	NULL	NULL	NULL
cnt_warp_speed_orders	BIGINT	YES	NULL	NULL	NULL
highest_warp_speed_issued	BIGINT	YES	NULL	NULL	NULL
bool_hand_phasers_fired	BIGINT	YES	NULL	NULL	NULL
bool_ship_phasers_fired	BIGINT	YES	NULL	NULL	NULL
bool_ship_photon_torpedos_fired	BIGINT	YES	NULL	NULL	NULL
cnt_transporter_pax	BIGINT	YES	NULL	NULL	NULL
cnt_damn_it_jim_quote	BIGINT	YES	NULL	NULL	NULL
cnt_im_givin_her_all_shes_got_quote	BIGINT	YES	NULL	NULL	NULL
cnt_highly_illogical_quote	BIGINT	YES	NULL	NULL	NULL
bool_enterprise_saved_the_day	BIGINT	YES	NULL	NULL	NULL