?????????????????????????????????????????????????????????????????Щ??????????
??????????????????????????????????????test????????test?????????????id??name??age??content??????????????????????????Щ????
????1 ????е?????????
????alter table test modify name varchar ??30????
????2 ???????
????alter table test add sex char(2);
????3 ????е?λ??
????alter table test modify content after name??
????4 ?????????????
????alter table test change age old tinyint??
????5 ?????
????alter table test drop sex??
????6 ?????
????drop table test??
????7 ????й???+????????
????create table test2 select * from test??
????8 ?????й???
????create table test3 like test??
????9 ????????
????insert into test3 select * from test??
????10 ?????????????????
????alter table test add constraint pk primary key ??id????
????11 ?????????????????
????alter table test drop primary key??
????12 ????????????????
????alter table test add constraint fk foreign key ??id?? references test2 ??id????
????13 ????????????????
????alter table test drop foreign key fk?????fk????????
????14 ?????????????????
????alter table test alter sex set default ‘f’??
????15 ?????????????????
????alter table test alter sex drop default??
????16 ???????????????
????alter table test modify name varchar??20?? not null??
?????????mysql??????У?????????????????????????????ó?not null????????null??????????????????????
????17 ???????????????
????alter table test add constraint checkname check??age>19????
??????mysql?У????????????????????????????????
????18  ?????????????????
????alter table test add constraint uq unique??name????
????19 ?????????????
????drop index uq on test??