Re: Efficient Boolean Storage

  Why worry if a boolean isn't a bit in database storage?
  When they are loaded to your CPU they will fill a register anyway (32
bits)

On Wed, 2002-12-04 at 14:01, Ericson Smith wrote:
> Hmmm...
>
> You can store them in an int4 type (will take up to 31)
>
> To store your numbers:
> $num = (2^$num1) + (2^$num2) ...
> where $num1 and $num2 are your bit positions that you want to set to
> "1",
>
> To retrieve them...
> SELECT * FROM table WHERE ((mycol & 2^1) != 0 OR (mycol & 2^3) != 0)
> Here you are checking for the 1st bit position and the 3rd bit position.
>
> - Ericson Smith
> eric@did-it.com
>
> On Wed, 2002-12-04 at 10:11, Richard Huxton wrote:
> > On Wednesday 04 Dec 2002 1:06 am, Chris White wrote:
> > > Hello,
> > >
> > > I need to store many (e.g. 30) booleans and am wondering what is the
> > > most efficient way to store them.  I can think of four options.
> > >
> > > Option 1...Use 'bool' data type
> > > No good since each value will require 1 byte rather than 1 bit.
> >
> > Depends what you're going to use them for. Are these 30 flags that should be
> > grouped together? Will the users/app want all together or one at a time? Will
> > they feature in WHERE clauses?
> >
> > --
> >   Richard Huxton
> >
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