{DESCRIBE | DESC} tbl_name [col_name | wild]
DESCRIBE provides information about the
columns in a table. It is a shortcut for SHOW COLUMNS
FROM. These statements also display information for
views. (See Section 13.5.4.3, “SHOW COLUMNS Syntax”.)
col_name can be a column name, or a
string containing the SQL ‘%’ and
‘_’ wildcard characters to obtain
output only for the columns with names matching the string.
There is no need to enclose the string within quotes unless it
contains spaces or other special characters.
mysql> DESCRIBE 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 | |
+------------+----------+------+-----+---------+----------------+
5 rows in set (0.00 sec)
Field indicates the column name.
The Null field indicates whether
NULL values can be stored in the column.
The Key field indicates whether the column is
indexed. A value of PRI indicates that the
column is part of the table's primary key.
UNI indicates that the column is part of a
UNIQUE index. The MUL
value indicates that multiple occurrences of a given value are
allowed within the column.
One reason for MUL to be displayed on a
UNIQUE index is that several columns form a
composite UNIQUE index; although the
combination of the columns is unique, each column can still hold
multiple occurrences of a given value. Note that in a composite
index, only the leftmost column of the index has an entry in the
Key field.
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. In the
example shown, the Extra field indicates that
the Id column was created with the
AUTO_INCREMENT keyword.
The DESCRIBE statement is provided for
compatibility with Oracle.
The SHOW CREATE TABLE and SHOW TABLE
STATUS statements also provide information about
tables. See Section 13.5.4, “SHOW Syntax”.
