Read-only fields in SQLite3 database table?

Question

I'm a beginner when it comes to databases and have been reading through the SQLite3 documentation. However, I can't find the answer to the following:

Is it possible to create a SQLite3 database table that has some read-only fields (i.e. not the whole of the table is read-only)?. I know I can stop people writing to the fields via some extra code, but I was wondering if can define a constraint or something similar.

Thanks!

Answer 1

You can create a trigger to prevent updates of specific columns:

CREATE TRIGGER ro_columns
BEFORE UPDATE OF col1, col2 ON mytable
BEGIN
    SELECT raise(abort, 'don''t do this!');
END

Answer 2

Sadly, constraints cannot be added after table creation in SQLite;

It is not possible to rename a column, remove a column, or add or remove constraints from a table.

In other words, no, you cannot make a column read only using a constraint, since creating the table with the (CHECK) constraint would make it impossible to add the read only values to the table in the first place.