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AskSQLTeam
Ask SQLTeam Question
0 Posts |
 Posted - 2005-12-05 : 08:16:47
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| jmhmaine writes "If SQL Server is storing the BIT data type as one bit, how does it store the absence of data, e.g. null values? Since a bit can only have two values, True/False or 0/1 how do does the Server track that bit is Null?" |
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madhivanan
Premature Yak Congratulator
22864 Posts |
Posted - 2005-12-05 : 08:29:38
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| If the bit column is defined as Null, SQL Server will store it as Null if no value is supplied to itMadhivananFailing to plan is Planning to fail |
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Arnold Fribble
Yak-finder General
1961 Posts |
Posted - 2005-12-05 : 08:38:30
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quote:
Originally posted by AskSQLTeam
jmhmaine writes "If SQL Server is storing the BIT data type as one bit, how does it store the absence of data, e.g. null values? Since a bit can only have two values, True/False or 0/1 how do does the Server track that bit is Null?"
The information about whether a column in a row contains NULL is stored in the row's NULL bitmap. At least, that's what Kalen Delaney says in Inside SQL Server 2000. And I believe her!Looking at this page http://msdn2.microsoft.com/en-us/library/ms178085.aspx it seems this is still the case in SQL Server 2005. |
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paulrandal
Yak with Vast SQL Skills
899 Posts |
Posted - 2005-12-05 : 12:00:04
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| One slight twist for SS2005, all columns have a bit in the NULL bitmap, regardless of whether they're NULLable or not, rathert han just the NULLable ones (SS2000). This makes a lot of things easier at negligible extra storage cost.Paul RandalLead Program Manager, Microsoft SQL Server Storage Engine(Legalese: This posting is provided "AS IS" with no warranties, and confers no rights.) |
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BIT Data Type Storage