Steps to reproduce:

1. Install an earlier version (e.g. 4.0)
2. Upgrade to the current stable (5.4.X)
3. Let it automatically update the database.

Result:

The database upgrade fails with a number of foreign key errors.

1. The error already reported at:
   https://support.zabbix.com/browse/ZBX-19435
2. Tries to add a column that already exists:

   [Z3005] query failed: [1060] Duplicate column name 'evaltype' [alter table `sysmaps_elements` add `evaltype` integer default '0' not null]
   

3. Tries to create a FK that already exists:

Can't create table `zabbix`.`#sql-2bf_3467` (errno: 121 "Duplicate key on write or update") [alter table `report_user` add constraint c_report_user_1 foreign key (`reportid`) references `report` (`reportid`) on delete cascade]

Expected:

Database script is idempotent: if the column/fk/object already exists, don't create it.

Include checks for whether this object already exists before creating it.