Re: bitwise storage and operations

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​Please include the list in all replies.

On Mon, Sep 26, 2016 at 4:14 PM, Jonathan Vanasco <postgres(at)2xlp(dot)com> wrote:

>
> On Sep 26, 2016, at 5:04 PM, David G. Johnston wrote:
>
> On Mon, Sep 26, 2016 at 1:44 PM, Jonathan Vanasco <postgres(at)2xlp(dot)com>
> wrote:
>
>> The documentation doesn't have any examples for SELECT for the bitwise
>> operators,
>
>
> That shows a simple computation. One can "SELECT" any computation and get
> a value.
>
> It doesn't show a bitwise operator being used against an INT or BIT
> column, as I further elaborated.
>

I assumed a certain level of familiarity with databases and provided enough
info to answer your main question: "what are the available bit string
operators?". That you can apply these operator to either constants or
columns was knowledge I took for granted.

> From what I can tell so far, i need to extract and compare a substring for
> the (reverse) index of the particular bit I want to filter on.
>

B'1001' is typed bit(4)...

The only requirement with a WHERE clause is that the computation must
result in a boolean. My example SELECT computation does just that. It
uses "varbit" for convenience but INT can be CAST() to BIT and the
operators themselves should operate on any of the BIT variants.

What you want is the "bit-wise AND" operator and the equality operator,
both of which you were shown.

I'd suggest you put forth your own example, filling in pseudo-code where
needed, if you wish for more specific advice.

David J.
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