ALTER TABLE projects ADD COLUMN code TEXT NOT NULL DEFAULT '';
ALTER TABLE projects ADD COLUMN ticket_seq INTEGER NOT NULL DEFAULT 0;

ALTER TABLE tickets ADD COLUMN number INTEGER;
ALTER TABLE tickets ADD COLUMN key TEXT NOT NULL DEFAULT '';

CREATE UNIQUE INDEX IF NOT EXISTS idx_projects_code ON projects(code) WHERE code != '';
CREATE UNIQUE INDEX IF NOT EXISTS idx_tickets_key ON tickets(key) WHERE key != '';
CREATE UNIQUE INDEX IF NOT EXISTS idx_tickets_project_number ON tickets(project_id, number) WHERE number IS NOT NULL;