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

mysql> SHOW INDEX FROM mytable FROM mydb;
mysql> SHOW INDEX FROM mydb.mytable;

Showing your Databases:
SHOW DATABASES lists the databases on the MySQL server host. You can also get this list using the mysqlshow command. 

mysql> SHOW DATABASES;

Showing your Tables:
SHOW TABLES lists the tables in a given database. You can also get this list using the 
mysqlshow db_name command. 

mysql> SHOW TABLES;

NOTE: If a user doesn't have any privileges for a table, the table will not show up in the output from SHOW TABLES or mysqlshow db_name. 

Showing the Columns of a Table:
SHOW COLUMNS lists the columns in a given table. If you specify the FULL option, 
you will also get the privileges you have for each column. If the column types are different than you expect them to be based on a CREATE TABLE statement, note that MySQL sometimes changes column types. 

mysql> SHOW COLUMNS from table_name;
or
mysql> SHOW FIELDS from table_name;
 

SHOW FIELDS is a synonym for SHOW COLUMNS, and SHOW KEYS is a 
synonym for SHOW INDEX. You can also list a table's columns or indexes with 
mysqlshow db_name tbl_name or mysqlshow -k db_name tbl_name.

SHOW INDEX returns the index information in a format that closely resembles the 
SQLStatistics call in ODBC. The following columns are returned: 

Showing the Index/Keys of a Table:
SHOW INDEX returns the index information in a format that closely resembles the 
SQLStatistics call in ODBC. SHOW KEYS is a synonym for SHOW INDEX

mysql> SHOW KEYS from table_name;
or
mysql> SHOW INDEX from table_name;