Qualcosa come
SELECT dataora,evento
FROM Tabella1
UNION
SELECT dataora,evento
FROM Tabella2
UNION
SELECT dataora,evento
FROM Tabella3
ORDER BY dataora
Qualcosa come
SELECT dataora,evento
FROM Tabella1
UNION
SELECT dataora,evento
FROM Tabella2
UNION
SELECT dataora,evento
FROM Tabella3
ORDER BY dataora