You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
set sql_safe_updates=0;
drop table t1,t2;
set timestamp=1038401397;
create table t1 (n int(10) not null primary key, d int(10), t timestamp);
create table t2 (n int(10) not null primary key, d int(10), t timestamp);
insert into t1 values(1,1,NULL);
insert into t2 values(1,10,NULL),(2,20,NULL);
set timestamp=1038000000;
UPDATE t1,t2 SET t1.d=t2.d WHERE t1.n=t2.n;
select * from t1;
n d t
1 10 20021123002000
select * from t2;
n d t
1 10 20021127154957
2 20 20021127154957
UPDATE t1,t2 SET 1=2 WHERE t1.n=t2.n;
You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near '1=2 WHERE t1.n=t2.n' at line 1
drop table t1,t2;
set timestamp=0;
set sql_safe_updates=0;
create table t1 (n int(10) not null primary key, d int(10));
create table t2 (n int(10) not null primary key, d int(10));
insert into t1 values(1,1), (3,3);
insert into t2 values(1,10),(2,20);
UPDATE t2 left outer join t1 on t1.n=t2.n SET t1.d=t2.d;
select * from t1;
n d
1 10
3 3
select * from t2;
n d
1 10
2 20
drop table t1,t2;
create table t1 (n int(10), d int(10));
create table t2 (n int(10), d int(10));
insert into t1 values(1,1),(1,2);
insert into t2 values(1,10),(2,20);
UPDATE t1,t2 SET t1.d=t2.d,t2.d=30 WHERE t1.n=t2.n;
select * from t1;
n d
1 10
1 10
select * from t2;
n d
1 30
2 20
drop table t1,t2;
create table t1 (n int(10), d int(10));
create table t2 (n int(10), d int(10));
insert into t1 values(1,1),(3,2);
insert into t2 values(1,10),(1,20);
UPDATE t1,t2 SET t1.d=t2.d,t2.d=30 WHERE t1.n=t2.n;
