Unique constraint Help

[chella]

Hi Experts,
I would like to know about the unique constraint in oracle. Please help me with an example.

Thanks in advance,
Chella

[vijaydiwakar]

Hi Experts,
I would like to know about the unique constraint in oracle. Please help me with an example.

Thanks in advance,
Chella

see there are two types of levels to apply contraints
1 is at column level
i.e. at the time of creation of tbl itself
like
create table temp(aa varchar2(1) unique);

and another is table level
i.e. after the tbl is created like
create table temp (aa varchar2(10));
alter table temp add constraint u_u unique(aa);

[gazeatvara]

see there are two types of levels to apply contraints
1 is at column level
i.e. at the time of creation of tbl itself
like
create table temp(aa varchar2(1) unique);

and another is table level
i.e. after the tbl is created like
create table temp (aa varchar2(10));
alter table temp add constraint u_u unique(aa);

Hi vijay

can we add unique constrain if the colum is already duplicated

[vijaydiwakar]

Hi vijay

can we add unique constrain if the colum is already duplicated

see we can't do that if column is alredy duplicated.
but in case of unique it provides u one blank
are u get my point how can u do it so??
think it