SHOW COLUMNS

Syntax

SHOW [FULL] {COLUMNS | FIELDS} FROM tbl_name [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW COLUMNS displays information about the columns in a given table. It also works for views. The LIKE clause, if present on its own, indicates which column names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

If the data types differ from what you expect them to be based on aCREATE TABLE statement, note that MariaDB sometimes changes data types when you create or alter a table. The conditions under which this occurs are described in the Silent Column Changes article.

The FULL keyword causes the output to include the column collation and comments, as well as the privileges you have for each column.

You can use db_name.tbl_name as an alternative to thetbl_name FROM db_name syntax. In other words, these two statements are equivalent:

SHOW COLUMNS FROM mytable FROM mydb;
SHOW COLUMNS FROM mydb.mytable;

SHOW COLUMNS displays the following values for each table column:

Field indicates the column name.

Type indicates the column data type.

Collation indicates the collation for non-binary string columns, or NULL for other columns. This value is displayed only if you use the FULL keyword.

The Null field contains YES if NULL values can be stored in the column, NO if not.

The Key field indicates whether the column is indexed:

• If Key is empty, the column either is not indexed or is indexed only as a secondary column in a multiple-column, non-unique index.

• If Key is PRI, the column is a PRIMARY KEY or is one of the columns in a multiple-column PRIMARY KEY.

• If Key is UNI, the column is the first column of a unique-valued index that cannot contain NULL values.

• If Key is MUL, multiple occurrences of a given value are allowed within the column. The column is the first column of a non-unique index or a unique-valued index that can contain NULL values.

If more than one of the Key values applies to a given column of a table, Key displays the one with the highest priority, in the order PRI, UNI, MUL.

A UNIQUE index may be displayed as PRI if it cannot contain NULL values and there is noPRIMARY KEY in the table. A UNIQUE index may display as MUL if several columns form a compositeUNIQUE index; although the combination of the columns is unique, each column can still hold multiple occurrences of a given value.

The Default field indicates the default value that is assigned to the column.

The Extra field contains any additional information that is available about a given column.

Value	Description
Value	Description
AUTO_INCREMENT	The column was created with the AUTO_INCREMENT keyword.
PERSISTENT	The column was created with the PERSISTENT keyword. (New in 5.3)
VIRTUAL	The column was created with the VIRTUAL keyword. (New in 5.3)
on update CURRENT_TIMESTAMP	The column is a TIMESTAMP column that is automatically updated on INSERT and UPDATE.

Privileges indicates the privileges you have for the column. This value is displayed only if you use the FULL keyword.

Comment indicates any comment the column has. This value is displayed only if you use the FULL keyword.

SHOW FIELDS is a synonym forSHOW COLUMNS. Also DESCRIBE and EXPLAIN can be used as shortcuts.

You can also list a table's columns with:

mariadb-show db_name tbl_name

See the mariadb-show command for more details.

The DESCRIBE statement provides information similar to SHOW COLUMNS. The information_schema.COLUMNS table provides similar, but more complete, information.

The SHOW CREATE TABLE, SHOW TABLE STATUS, and SHOW INDEX statements also provide information about tables.

Examples

SHOW COLUMNS FROM city;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| Name       | char(35) | NO   |     |         |                |
| Country    | char(3)  | NO   | UNI |         |                |
| District   | char(20) | YES  | MUL |         |                |
| Population | int(11)  | NO   |     | 0       |                |
+------------+----------+------+-----+---------+----------------+

SHOW COLUMNS FROM employees WHERE Type LIKE 'Varchar%';
+---------------+-------------+------+-----+---------+-------+
| Field         | Type        | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+-------+
| first_name    | varchar(30) | NO   | MUL | NULL    |       |
| last_name     | varchar(40) | NO   |     | NULL    |       |
| position      | varchar(25) | NO   |     | NULL    |       |
| home_address  | varchar(50) | NO   |     | NULL    |       |
| home_phone    | varchar(12) | NO   |     | NULL    |       |
| employee_code | varchar(25) | NO   | UNI | NULL    |       |
+---------------+-------------+------+-----+---------+-------+

See Also

• DESCRIBE

• mariadb-show

• SHOW CREATE TABLE

• SHOW TABLE STATUS

• SHOW INDEX

• Extended SHOW

• Silent Column Changes

_{This page is licensed: GPLv2, originally from fill_help_tables.sql}