SQLite's ALTER TABLE can not DROP unnamed CHECK constraints

As of SQLite 3.53.3, DROP CONSTRAINT only works on named constraints like CONSTRAINT name CHECK(...).

The new ALTER TABLE features enable removing and adding constraints to a schema without the usual dance of creating, populating and renaming temporary tables. Unfortunately however, this does not work for constraints defined like this:

CREATE TABLE Things(
     one_column INTEGER NOT NULL CHECK (the_column IN (0, 1))
    , two_column INTEGER
    , CHECK (two_column > 0 OR two_column IS NULL)
) STRICT;

You need to give every constraint a name to be able to change them in migrations:

CREATE TABLE Things(
     one_column INTEGER NOT NULL 
      CONSTRAINT one_is_good CHECK (one_column IN (0, 1))
    , two_column INTEGER
      CONSTRAINT two_is_good CHECK (two_column > 0 OR two_column IS NULL)
    , CONSTRAINT all_is_good CHECK (one_column + two_column = 3)
) STRICT;

Now you can remove and add constraints:

ALTER TABLE Things DROP CONSTRAINT one_is_good;

ALTER TABLE Things ADD CONSTRAINT even_better CHECK (one_column > 100);

Source: sqlite/alter.c. SQLite stores the schema as the literal DDL string used to create it, and ALTER TABLE operations modify these table definitions in text form. The linked function needs a CONSTRAINT token to do anything, and a plain CHECK is not handled.