Table t1 (f1, f2). Primary key (f1, f2) Contents : ('1', 'one') and
('2' , 'two')
Table t2. Same as t1. Same key, same data.

I ran : select t1.f1 from t1 t1, t2 t2
where exists (
select 1 from dual where t1.f1 = t2.f1
)
I used 'dual' because 'null' did not work in its place; I was just
trying out things.
This TOAD query/window hanged.

I opened another window, and ran :
update t1 set f1 = 'new' ;
commit ;
insert into t1 select * from t2 ;

I get the error : Primary Key Constraint Violation.
I suspect that that hanged query has something to do with this problem.

Please advise. TIA.

dn.usenet wrote:
> Table t1 (f1, f2). Primary key (f1, f2) Contents : ('1', 'one') and
> ('2' , 'two')
> Table t2. Same as t1. Same key, same data.
>
> I ran : select t1.f1 from t1 t1, t2 t2
> where exists (
> select 1 from dual where t1.f1 = t2.f1
> )
> I used 'dual' because 'null' did not work in its place; I was just
> trying out things.
> This TOAD query/window hanged.
>

By the way, I know what command to use to see rows with t1.f1 = t2.f1
without using 'where exists' or 'dual'. I was just trying out those
things
out of curiosity.

You have a duplicate key error because you are trying to insert a
duplicate key. This has nothing to do the hung query. A duplicate is
a duplicate.

HTH -- Mark D Powell --