On Fri, 20 Jul 2007, Kathey Marsden wrote:
Ravinder Reddy wrote:
hi all,
w.r.t DERBY-2945(convert lang/primarykey.sql to junit)
I have a small doubt.
There is a test for verifying a unique key can not contain nulls.
1)-- verify that a unique key can not contain nulls
create table pos1 (c1 int not null unique, c2 int);
insert into pos1 (c1) values(null);
insert into pos1 (c1) values(null);
select * from pos1;
drop table pos1;
And It tests that null values are not allowed in c1.
Irrespective of uniqueness , c1 can't contain null values as it is
defined as not null.It seems that the test is wrong.
The test seems reasonable enough, but I guess it is really testing that
not null works #:)
We could have a test like the one below if we don't have one already.
ij> create table pos1 (c1 int unique, c2 int);
ERROR 42831: 'C1' cannot be a column of a primary key or unique key
because it can contain null values.
2) I am shocked to know that Derby doesn't allow a unique key column to
contain NULL values.can some somebody justify it.?
You are easily shocked #:)
I think most of the database systems(oracle , db2 , mySql ,
postgreSQL et al) allow a unique key column to contain NULL values.
That's why I am shocked..!!!!!
Thank You.
Kathey
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Every problem that has been solved can be solved again in a better way
- Ravinder Reddy
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