Syntax:
SHOW INDEX FROM tbl_name [FROM db_name]

SHOW INDEX returns table index information. The format resembles that
of the SQLStatistics call in ODBC.
The LIKE clause, if present, indicates which event names to match. The
WHERE clause can be given to select rows using more general conditions,
as discussed in
http://dev.mysql.com/doc/refman/5.0/en/extended-show.html.

You can use db_name.tbl_name as an alternative to the tbl_name FROM
db_name syntax. These two statements are equivalent:

SHOW INDEX FROM mytable FROM mydb;
SHOW INDEX FROM mydb.mytable;

SHOW KEYS is a synonym for SHOW INDEX. You can also list a table's
indexes with the mysqlshow -k db_name tbl_name command.

URL: http://dev.mysql.com/doc/refman/5.0/en/show-index.html

