SQLITE_CANTOPEN is returned mainly in the OS abstraction layer (meaning something with file/directory access permissions is probably broken) and in the Pager and the WAL code.

Apart from that the only thing that comes to mind with views is the not so recent limitation that views may only reference tables residing in the same file.

E.g. CREATE VIEW a.myview ... AS SELECT ... FROM b.mytable ...

is only valid if database b is attached before database a, making database a "unopenable" alone (or after mytable is dropped).

Just to chime in on this one, I'm seeing the exact same behavior on two VM's running Windows Server 2019. I have no idea (yet) how to trigger the behavior, but once it 'happens' I can reliable reproduce (see details below). Then at some point (some hourse), the behavior is gone, a little while later (some hours) it's back, etc.

It's not user restriction related, I have tried several directories, all showing the same behavior.

I've not been able to reproduce since I found this thread, so I haven't tried the suggestions given by Dan yet.

I have two tables which look like this:

-- Table: Items
CREATE TABLE Items (
    ID              INTEGER  PRIMARY KEY AUTOINCREMENT,
    Status TEXT,
    LogTime         DATETIME,
    ItemID  TEXT
);


-- Table: Data
CREATE TABLE Data (
    DataID      REFERENCES Items (ID) ON DELETE CASCADE,
    Name                TEXT,
    Value               TEXT
);

When this is occuring, this query doesn't work:

  SELECT ItemID
  FROM 
   (
    select 
     * 
    FROM 
     Items a 
    INNER JOIN 
     Data g 
     ON  a.ID = g.DataID 
    WHERE 
     a.Status in ('Some status') 
   ) r1 
   GROUP by r1.ID
  ;

It does work however when I change it to:

  SELECT ID
  FROM 
   (
    select 
     * 
    FROM 
     Items a 
    INNER JOIN 
     Data g 
     ON  a.ID = g.DataID 
    WHERE 
     a.Status in ('Some status') 
   ) r1 
   GROUP by r1.ID
  ;

What I've figured out now is that the reason this stops working for me (this time) is that TEMP environment variable points to c:\users\<username>\AppData\Local\Temp\1

The number at the end may vary. When this isn't working it is because that subdir (1) in the 'normal' temp dir isn't there (c:\users\<username>\AppData\Local\Temp exists, c:\users\<username>\AppData\Local\Temp\1 does not). When I create the sub dir the error goes away.

I have no clue (yet) why this subdir sometimes isn't, and sometimes is there. When I log out and back in again, the environment variable is set to something else (other number in the end) and the directory is there.

For other people finding themselves in this situation, can you please check if this is the same for you?