Roles were introduced in MariaDB 10.0.5.
 
Syntax
------ 
DROP ROLE [IF EXISTS] role_name [,role_name ...]
 
Description
----------- 
The DROP ROLE statement removes one or more MariaDB roles.
To use this
statement, you must have the global CREATE USER privilege or
the DELETE privilege for the mysql database.
 
DROP ROLE does not disable roles for connections which
selected them with SET ROLE. If a role has previously been
set as a default role, DROP ROLE does not remove the record
of the default role from the mysql.user table. If the role
is subsequently recreated and granted, it will again be the
user's default. Use SET DEFAULT ROLE NONE to explicitly
remove this.
 
If any of the specified user accounts do not exist, ERROR
1396 (HY000)
results. If an error occurs, DROP ROLE will still drop the
roles that
do not result in an error. Only one error is produced for
all roles which have not been dropped:
 
ERROR 1396 (HY000): Operation DROP ROLE failed for
'a','b','c'
 
Failed CREATE or DROP operations, for both users and roles,
produce the same error code.
 
Before MariaDB 10.1.13, the DROP ROLE statement was not
permitted in prepared statements.
 
IF EXISTS
 
The IF EXISTS clause was added in MariaDB 10.1.3
 
If the IF EXISTS clause is used, MariaDB will return a
warning instead of an error if the role does not exist.
 
Examples
-------- 
DROP ROLE journalist;
 
The same thing using the optional IF EXISTS clause:
 
DROP ROLE journalist;
 
ERROR 1396 (HY000): Operation DROP ROLE failed for
'journalist'
 
DROP ROLE IF EXISTS journalist;
 
Query OK, 0 rows affected, 1 warning (0.00 sec)
 
Note (Code 1975): Can't drop role 'journalist'; it
doesn't exist
 


URL: https://mariadb.com/kb/en/drop-role/