ORA-01219: database not open: queries allowed on fixed tables/views only

If the problem is related to a pluggable database then you can do the following:

1. Check the status of the PDB

> SELECT name, open_mode FROM v$pdbs ORDER BY name;

NAME      OPEN_MODE
-------------------
ORCLPDB   MOUNTED

2. Change the status to OPEN if it is not (like MOUNTED for example)

ALTER PLUGGABLE DATABASE orclpdb OPEN READ WRITE;

just in case if someone comes to here for this question

RECOVER DATABASE; and then ALTER DATABASE OPEN;

fixed my issue.

SQL>

ALTER DATABASE OPEN;
ALTER DATABASE OPEN *

ERROR at line 1:
ORA-01113: file 1 needs media recovery
ORA-01110: data file 1: 'C:\APP\ADMINISTRATOR\ORADATA\WIND\SYSTEM01.DBF'

First of all check the status of the instance you work with (this may need to connect under administrator account):

select status from v$instance;

Probably you will get

STATUS
------------
MOUNTED

Under sys account try to complete

ALTER DATABASE OPEN;

and check that it's completed successfuly. If not - please share the result of output and alert log in your question.