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drop table if exists t1,t2;
create table t1 (id integer, x integer) engine=INNODB;
insert into t1 values(0, 0);
set autocommit=0;
SELECT * from t1 where id = 0 FOR UPDATE;
id x
0 0
set autocommit=0;
update t1 set x=2 where id = 0;
update t1 set x=1 where id = 0;
select * from t1;
id x
0 1
commit;
commit;
select * from t1;
id x
0 2
commit;
drop table t1;
create table t1 (id integer, x integer) engine=INNODB;
create table t2 (b integer, a integer) engine=INNODB;
insert into t1 values(0, 0), (300, 300);
insert into t2 values(0, 10), (1, 20), (2, 30);
commit;
set autocommit=0;
select * from t2;
b a
0 10
1 20
2 30
update t2 set a=100 where b=(SELECT x from t1 where id = b FOR UPDATE);
select * from t2;
b a
0 100
1 20
2 30
select * from t1;
id x
0 0
300 300
set autocommit=0;
update t1 set x=2 where id = 0;
update t1 set x=1 where id = 0;
select * from t1;
id x
0 1
300 300
commit;
commit;
select * from t1;
id x
0 2
300 300
commit;
drop table t1, t2;
create table t1 (id integer, x integer) engine=INNODB;
create table t2 (b integer, a integer) engine=INNODB;
insert into t1 values(0, 0), (300, 300);
insert into t2 values(0, 0), (1, 20), (2, 30);
commit;
select a,b from t2 UNION SELECT id, x from t1 FOR UPDATE;
a b
0 0
20 1
30 2
300 300
select * from t2;
b a
0 0
1 20
2 30
select * from t1;
id x
0 0
300 300
update t2 set a=2 where b = 0;
select * from t2;
b a
0 2
1 20
2 30
update t1 set x=2 where id = 0;
update t1 set x=1 where id = 0;
select * from t1;
id x
0 1
300 300
commit;
commit;
select * from t1;
id x
0 2
300 300
commit;
drop table t1, t2;
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