On 18 Jul 2019, at 5:02pm, Alexandre Billon <[email protected]> wrote:
> INSERT INTO sales ("client", "salesman", "revenue")
> VALUES ('C1', NULL, 10.0);
The value NULL in SQLite means 'value unknown'. It is a special case. If you
compare two NULLs SQLite will act as if those values are different. Therefore
you can have two PRIMARY KEYs with NULL in the same place.
<https://www.sqlite.org/nulls.html>
> sqlite> INSERT INTO sales ("client", "salesman", "revenue")
> ...> VALUES ('C1', '', 10.0);
> sqlite>
> sqlite> INSERT INTO sales ("client", "salesman", "revenue")
> ...> VALUES ('C1', '', 10.0);
> Error: UNIQUE constraint failed: sales.client, sales.salesman
As you see here when you try the sme thing with non-NULL values, you get the
error you expected.
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