DROP TABLE IF EXISTS t1; CREATE TABLE t1 ( pk1 INT NOT NULL PRIMARY KEY, b INT NOT NULL, c INT NOT NULL UNIQUE ) ENGINE=ndbcluster; INSERT INTO t1 VALUES (0, 1, 0),(1,2,1),(2,3,2); UPDATE t1 set b = c; select * from t1 order by pk1; pk1 b c 0 0 0 1 1 1 2 2 2 UPDATE t1 set pk1 = 4 where pk1 = 1; select * from t1 order by pk1; pk1 b c 0 0 0 2 2 2 4 1 1 UPDATE t1 set pk1 = 4 where pk1 = 2; ERROR 23000: Duplicate entry '4' for key 'PRIMARY' UPDATE IGNORE t1 set pk1 = 4 where pk1 = 2; select * from t1 order by pk1; pk1 b c 0 0 0 2 2 2 4 1 1 UPDATE t1 set pk1 = 1, c = 2 where pk1 = 4; ERROR 23000: Duplicate entry '' for key '*UNKNOWN*' UPDATE IGNORE t1 set pk1 = 1, c = 2 where pk1 = 4; select * from t1 order by pk1; pk1 b c 0 0 0 2 2 2 4 1 1 UPDATE t1 set pk1 = pk1 + 10; select * from t1 order by pk1; pk1 b c 10 0 0 12 2 2 14 1 1 DROP TABLE IF EXISTS t1;