On 2014/10/13 13:52, Paul Sanderson wrote:
I have a table with an integer value which is a bitmask. one or more of the
bits can be set and each bit has a corresponding meaning.
so using the windows file attribute as an example we have
0c01 readonly
0x02 hidden
0x04 system
0x10 directory
0x20 archive
none, any or all could be set
I'd like to create a query which would take an attribute, say 0x07 and spit
out "system, hidden, readonly"
Or you could make a table like this:
CREATE TABLE "fileFlags" (
"ID" INTEGER PRIMARY KEY,
"Descr" TEXT
);
Populate it with the Mask descriptions like so:
INSERT INTO "fileFlags" ("ID","Descr") VALUES
(1,'readonly'),
(2,'hidden'),
(4,'system'),
(8,'unknown'),
(16,'directory'),
(32,'archive');
And then any query of the form:
SELECT F.Descr FROM fileFlags AS F WHERE (F.ID & [BitValue])>0;
Will work, as the following tests shown:
SELECT F.Descr FROM fileFlags AS F WHERE (F.ID & 11)>0
readonly
hidden
unknown
SELECT F.Descr FROM fileFlags AS F WHERE (F.ID & 7)>0
readonly
hidden
system
SELECT F.Descr FROM fileFlags AS F WHERE (F.ID & 4)>0
system
etc.
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