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The SHOW COLUMNS statement shows details about columns in a table, including each column's name, type, default value, and whether or not it's nullable.
Required privileges
The user must have any privilege on the target table.
Synopsis
Parameters
| Parameter | Description |
|---|---|
table_name |
The name of the table for which to show columns. |
Response
The following fields are returned for each column.
| Field | Description |
|---|---|
column_name |
The name of the column. |
data_type |
The data type of the column. |
is_nullable |
Whether or not the column accepts NULL. Possible values: true or false. |
column_default |
The default value for the column, or an expression that evaluates to a default value. |
generation_expression |
The expression used for a computed column. |
indices |
The list of indexes that the column is involved in, as an array. |
is_hidden |
Whether or not the column is hidden. Possible values: true or false. |
Examples
Setup
The following examples use MovR, a fictional vehicle-sharing application, to demonstrate CockroachDB SQL statements. For more information about the MovR example application and dataset, see MovR: A Global Vehicle-sharing App.
To follow along, run cockroach demo to start a temporary, in-memory cluster with the movr dataset preloaded:
$ cockroach demo
Show columns in a table
> SHOW COLUMNS FROM users;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-----------+-------------+----------------+-----------------------+--------------------------+------------
id | UUID | false | NULL | | {primary,users_name_idx} | false
city | VARCHAR | false | NULL | | {primary,users_name_idx} | false
name | VARCHAR | true | NULL | | {primary,users_name_idx} | false
address | VARCHAR | true | NULL | | {primary} | false
credit_card | VARCHAR | true | NULL | | {primary} | false
(5 rows)
Alternatively, within the built-in SQL shell, you can use the \d <table> shell command:
> \d users
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
+-------------+-----------+-------------+----------------+-----------------------+-----------+-----------+
id | UUID | false | NULL | | {primary,users_name_idx} | false
city | VARCHAR | false | NULL | | {primary,users_name_idx} | false
name | VARCHAR | true | NULL | | {primary,users_name_idx} | false
address | VARCHAR | true | NULL | | {primary} | false
credit_card | VARCHAR | true | NULL | | {primary} | false
(5 rows)
Show columns with comments
You can use COMMENT ON to add comments on a column.
> COMMENT ON COLUMN users.credit_card IS 'This column contains user payment information.';
> SHOW COLUMNS FROM users WITH COMMENT;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden | comment
+-------------+-----------+-------------+----------------+-----------------------+-----------+-----------+------------------------------------------------+
id | UUID | false | NULL | | {primary} | false | NULL
city | VARCHAR | false | NULL | | {primary} | false | NULL
name | VARCHAR | true | NULL | | {primary} | false | NULL
address | VARCHAR | true | NULL | | {primary} | false | NULL
credit_card | VARCHAR | true | NULL | | {primary} | false | This column contains user payment information.
(5 rows)
