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| From | Erland Sommarskog <esquel@sommarskog.se> |
| Newsgroups | comp.databases.ms-sqlserver |
| Subject | Re: How to determine true contents of not null columns that display as empty |
| Date | Thu, 07 Mar 2013 22:55:55 +0100 |
| Organization | Erland Sommarskog |
| Lines | 22 |
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Mark D Powell (Mark.Powell2@hp.com) writes: > How can a "not null" colummn be empty? Can anyone explain what I am > seeing and where specifically in the documentation I can read up on > this? NULL and the empty string are not the same thing. NULL is an unknown value, for which three-valued logic applies. All comparisons with NULL yield UNKNOWN, even NULL = NULL. Since the values are unknown, we can't tell whether the two values are same or not. An empty string on the other hand is a known value: a string with zero characters. -- Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se Links for SQL Server Books Online: SQL 2008: http://msdn.microsoft.com/en-us/sqlserver/cc514207.aspx SQL 2005: http://msdn.microsoft.com/en-us/sqlserver/bb895970.aspx
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How to determine true contents of not null columns that display as empty Mark D Powell <Mark.Powell2@hp.com> - 2013-03-07 09:16 -0800
Re: How to determine true contents of not null columns that display as empty rja.carnegie@gmail.com - 2013-03-07 09:29 -0800
Re: How to determine true contents of not null columns that display as empty Erland Sommarskog <esquel@sommarskog.se> - 2013-03-07 22:55 +0100
Re: How to determine true contents of not null columns that display as empty rja.carnegie@gmail.com - 2013-03-07 15:06 -0800
Re: How to determine true contents of not null columns that display as empty Mark D Powell <Mark.Powell2@hp.com> - 2013-03-14 10:56 -0700
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