SQLite 3.39

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CREATE TABLE Fooey(SomeInteger PRIMARY KEY);
✓
INSERT INTO Fooey(SomeINteger) VALUES (NULL);
✓
INSERT INTO Fooey(SomeINteger) VALUES (NULL);
✓
select * from fooey;

SomeInteger

null

null

INSERT INTO Fooey(SomeInteger) VALUES (33);
✓
INSERT INTO Fooey(SomeInteger) VALUES (44);
✓
INSERT INTO Fooey(SomeInteger) VALUES (33);

{
  "code": "SQLITE_CONSTRAINT_PRIMARYKEY"
}

select * from fooey;

SomeInteger

null

null

33

44

SomeInteger
null
null

SomeInteger
null
null
33
44