debra f wrote:
What's the best way to do a bitwise comparison in a sql query
such as the one indicated below - for example - i have one
Indicator field (currently defined as numeric) in my table which
is being used to store a variety of indicators (rather than
having a slew of boolean columns)
eg (random examples):
byte 1 indicates IsRetired (val 1)
byte 2 indicates IsOnDisability (val 2)
...
byte 4 indicates IsOverSixFeetTall (val 8)
ex: if the Indicator value = 9 (byte 1001) then IsRetired = true
,IsOnDisability = false and IsOverSixFeetTall = true
In vb - to determine whether a hex flag is on or not, we do a
bitwise comparison such as
IsRetired = (Indicator and 1)
IsOnDisability = (Indicator and 2)
IsOverSixFeetTall = (Indicator and 8)
How do I mimic this sort of behavior in sqlite?
For example -
Select * from MyTable Where (Indicator and 1)
Any help is appreciated.
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Debra,
You need the bitwise operators & (and), | (or), and ~ (not).
IsRetired = (Indicator & 1)
IsOnDisability = (Indicator & 2)
IsOverSixFeetTall = (Indicator & 8)
These values will be non-zero if the condition is true.
Select * from MyTable Where Indicator & 1;
You use the | operator to set the condition and & with the complement to clear.
Update MyTable
set Indicator = Indicator | 1, -- set IsRetired
set Indicator = Indiocator & ~2 -- clear IsOnDisability
where Indicator & 8
HTH
Dennis Cote
