I built the database with the following command
mysql -u root -p mysql
mysql> CREATE DATABASE netxms;
mysql> GRANT ALL ON netxms.* TO netxms@localhost IDENTIFIED BY 'netxms';
mysql> \q
And I also want to install the database with the following error that I encounter
root@debian:~# nxdbmgr init /usr/share/netxms/sql/dbinit_mysql.sql
NetXMS Database Manager Version 2.2.4 Build 9506 (2.2.4) (UNICODE)

Initializing database...
SQL query failed (Specified key was too long; max key length is 767 bytes):
CREATE TABLE userdb_custom_attributes (  object_id integer not null,  attr_name varchar(255) not null,  attr_value longtext not null,  PRIMARY KEY(object_id,attr_name) )
Database initialization failed

The version number of the database used in my system is automatically installed with the above command

root@debian:~# mysql
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 9
Server version: 10.1.26-MariaDB-0+deb9u1 Debian 9.1

Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> SHOW VARIABLES LIKE "%version%";
+-------------------------+--------------------------+
| Variable_name          | Value                    |
+-------------------------+--------------------------+
| innodb_version          | 5.6.36-82.1              |
| protocol_version        | 10                      |
| slave_type_conversions  |                          |
| version                | 10.1.26-MariaDB-0+deb9u1 |
| version_comment        | Debian 9.1              |
| version_compile_machine | x86_64                  |
| version_compile_os      | debian-linux-gnu        |
| version_malloc_library  | system jemalloc          |
| version_ssl_library    | YaSSL 2.4.2              |
| wsrep_patch_version    | wsrep_25.19              |
+-------------------------+--------------------------+
10 rows in set (0.00 sec)

please guide me