CREATE TABLE IF NOT EXISTS graph_viewport
(
    id         INTEGER PRIMARY KEY CHECK (id = 1),
    zoom       REAL NOT NULL CHECK (zoom = zoom AND zoom > 0),
    offset_x   REAL NOT NULL CHECK (offset_x = offset_x),
    offset_y   REAL NOT NULL CHECK (offset_y = offset_y),
    updated_at TEXT NOT NULL CHECK (length(updated_at) = 20)
);