Re: BUG #1698: Different behavior in UNIQUE and DISTINCT

On Thu, Jun 02, 2005 at 20:22:07 +0100,
Mauro Delfino <maurodelfino(at)gmail(dot)com> wrote:
>
> I have the these two tables:
> CREATE TABLE table_one
> ( field1 VARCHAR(255) );
>
> CREATE TABLE table_two
> ( field1 VARCHAR(255) UNIQUE );
>
> table_one has 500k records. I certify that all strings are distinct with
> this query:
> SELECT DISTINCT field1 FROM table_one;
> The query results 500k rows.
>
> But if I try to insert the records of table_one into table_two with the
> following command:
> INSERT INTO table_two (field1) (SELECT field1 FROM table_one);
> This error occurs:
> ERROR: duplicate key violates unique constraint "table_two_field1_key"
>
> What happened? DISTINC and UNIQUE have different algorithms to determine
> when two strings are equal?

Are you sure table_two is empty when you do this?