MariaDB 10.3

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CREATE TABLE service (id INT, stamp TIMESTAMP(3));
INSERT INTO service (id, stamp) VALUES (1, CURRENT_TIMESTAMP(3));
SELECT * FROM service;

id
stamp

1
2025-06-10 09:47:51.366

INSERT INTO service (id, stamp) VALUES (2, CURRENT_TIMESTAMP(3));
SELECT t1.stamp - t2.stamp elapsed
FROM service t1
CROSS JOIN service t2
WHERE t1.id = 2 AND t2.id = 1;

elapsed

0.007