There is a bug in monetdb, you can run the following script in two clients(mclient.exe), and before test, please disable autocommit option. user A: USER B: CREATE TABLE TEST(C1 INT PRIMARY KEY, C2 INT); INSERT INTO TEST VALUES(1,1); COMMIT; SELECT C2 FROM TEST WHERE C1=1; SELECT C2 FROM TEST WHERE C1=1; UPDATE TEST SET C2=10 WHERE C1=1; UPDATE TEST SET C2=30 WHERE C1=1; COMMIT; COMMIT;--CONFLICT, NEED TO ROLLBACK; ROLLBACK; UPDATE TEST SET C2=30 WHERE C1=1; SELECT C2 FROM TEST WHERE C1=1; --THE RESULT IS 10, NOT 30. TOO BAD! 2010-03-09 oursql