Matthew Wilson wrote:
I'm trying to comprehend how NULL values interact with unique indexes.
It seems like I can insert two rows with NULL values in a column with a
unique constraint just fine.
Is there something special about NULL? Can anyone post some links to
explain what is going on?
When you think of null as "unknown", it makes sense.
Does an unknown value equal another unknown value?
http://www.postgresql.org/docs/8.3/interactive/functions-logical.html
http://www.postgresql.org/docs/8.3/interactive/functions-comparison.html
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