Можете да направите UNION вместо. По този начин не генерирате ненужни редове
SELECT country, start_date,
CASE WHEN event_date BETWEEN start_date AND end_date
THEN event_date - 1
ELSE end_date
END AS end_date, event_date
FROM table1
UNION ALL
SELECT country, event_date, end_date, event_date
FROM table1
WHERE event_date BETWEEN start_date AND end_date
ORDER BY country, start_date, end_date, event_date
Ето SQLFiddle демонстрация
Изход:
<преди>| държава | начална_дата | крайна_дата | дата_на събитие ||---------|------------|------------|----------- -|| A | 1960-01-01 | 19.07.1994 | 1994-07-20 || A | 1994-07-20 | 1999-12-31 | 1994-07-20 || B | 1926-01-01 | 1995-12-31 | (null) |
