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Rev

I'd your answer can be considered correct from function perspective (within SQL Server domain). BUT, you are wrong in understanding the concept of "index" and "key". To me, it is like you compare apple with orange. They are really different even if both are sweet and juicy.

jyao
– jyao

2016-09-13 23:51:13 +00:00
Commented Sep 13, 2016 at 23:51
Strictly speaking, a SQL Server unique index can contain a NULL value. It goes against the SQL spec by having unique indices disallow more than one instance of a NULL value. You can use filtered indices to simulate ANSI behavior, though.

Jon of All Trades
– Jon of All Trades

2018-08-28 21:57:39 +00:00
Commented Aug 28, 2018 at 21:57

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