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create table t1 (v varchar(32) not null);
insert into t1 values ('def'),('abc'),('hij'),('3r4f');
select * from t1;
v
3r4f
abc
def
hij
alter table t1 change v v2 varchar(32);
select * from t1;
v2
3r4f
abc
def
hij
alter table t1 change v2 v varchar(64);
select * from t1;
v
3r4f
abc
def
hij
update t1 set v = 'lmn' where v = 'hij';
select * from t1;
v
3r4f
abc
def
lmn
alter table t1 add i int auto_increment not null primary key first;
select * from t1;
i v
1 def
2 abc
3 lmn
4 3r4f
update t1 set i=5 where i=3;
select * from t1;
i v
1 def
2 abc
4 3r4f
5 lmn
alter table t1 change i i bigint;
select * from t1;
i v
1 def
2 abc
4 3r4f
5 lmn
alter table t1 add unique key (i, v);
select * from t1 where i between 2 and 4 and v in ('def','3r4f','lmn');
i v
4 3r4f
drop table t1;
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