# # BUG#6236 - ALTER TABLE MODIFY should set implicit NOT NULL on PK columns # create table t1 ( a varchar(10) not null primary key ) engine=myisam; create table t2 ( a varchar(10) not null primary key ) engine=merge union=(t1); flush tables; alter table t1 modify a varchar(10); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `a` varchar(10) NOT NULL, PRIMARY KEY (`a`) ) ENGINE=MRG_MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci UNION=(`t1`) flush tables; alter table t1 modify a varchar(10) not null; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `a` varchar(10) NOT NULL, PRIMARY KEY (`a`) ) ENGINE=MRG_MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci UNION=(`t1`) drop table if exists t1, t2;