import sqlite3
with sqlite3.connect(":memory:") as db:
    db.execute("CREATE TABLE daily (day TEXT PRIMARY KEY, litres REAL NOT NULL CHECK(litres >= 0))")
    db.executemany("INSERT INTO daily VALUES (?, ?)", [("2026-05-04", 18.), ("2026-05-05", 22.)])
    count, total = db.execute("SELECT COUNT(*), SUM(litres) FROM daily").fetchone()
    assert count == 2 and total == 40.
    print("Two daily rows; period total 40.0 litres")