Sí, puedes comparar una datetime con una timestamp . No está mal, pero ten en cuenta lo siguiente:
De Manual de referencia de MySQL ::Los tipos DATETIME, DATE y TIMESTAMP .
Tenga en cuenta cómo los siguientes casos de prueba funcionan bien:
CREATE TABLE t1 (d1 datetime, d2 timestamp);
INSERT INTO t1 VALUES ('1968-01-01 00:00:00', '1980-01-01 00:00:00');
INSERT INTO t1 VALUES ('2040-01-01 00:00:00', '1980-01-01 00:00:00');
SELECT * FROM t1 WHERE d2 < d1;
+---------------------+---------------------+
| d1 | d2 |
+---------------------+---------------------+
| 2040-01-01 00:00:00 | 1980-01-01 00:00:00 |
+---------------------+---------------------+
1 row in set (0.00 sec)
SELECT * FROM t1 WHERE d2 > d1;
+---------------------+---------------------+
| d1 | d2 |
+---------------------+---------------------+
| 1968-01-01 00:00:00 | 1980-01-01 00:00:00 |
+---------------------+---------------------+
1 row in set (0.00 sec)
SELECT * FROM t1 WHERE d2 < '2040-01-01 00:00:00';
+---------------------+---------------------+
| d1 | d2 |
+---------------------+---------------------+
| 1968-01-01 00:00:00 | 1980-01-01 00:00:00 |
| 2040-01-01 00:00:00 | 1980-01-01 00:00:00 |
+---------------------+---------------------+
2 rows in set (0.00 sec)
SELECT * FROM t1 WHERE d2 > '2040-01-01 00:00:00';
Empty set (0.00 sec)
