drop table if exists t1,t2; create table t1(a int, unique(a)); insert into t1 values(2); create table t2(a int); insert into t2 values(1),(2); reset master; insert into t1 select * from t2; ERROR 23000: Duplicate entry '2' for key 'a' show binlog events; Log_name Pos Event_type Server_id End_log_pos Info master-bin.000001 4 Format_desc 1 106 Server ver: VERSION, Binlog ver: 4 master-bin.000001 106 Query 1 200 use `test`; insert into t1 select * from t2 select * from t1; a 1 2 drop table t1, t2; create table t1(a int); insert into t1 values(1),(1); reset master; create table t2(unique(a)) select a from t1; ERROR 23000: Duplicate entry '1' for key 'a' show binlog events; Log_name Pos Event_type Server_id End_log_pos Info master-bin.000001 4 Format_desc 1 106 Server ver: VERSION, Binlog ver: 4 drop table t1;