Bitmask Handling, part 4: Left-shift and right-shift

re: Bitmask Handling, part 4: Left-shift and right-shift

saisub — Tue, 27 Mar 2007 03:47:55 GMT

no info regarding signed number shift..bye

re: Bitmask Handling, part 4: Left-shift and right-shift

Adam Machanic — Tue, 22 May 2007 18:05:10 GMT

Sorry, I kind of dropped the ball on this over two years ago. Some day perhaps I'll revisit it, but no promises. I'll probably use SQLCLR if I do.

re: Bitmask Handling, part 4: Left-shift and right-shift

Stephen Channell — Thu, 22 May 2008 12:58:13 GMT

Have I missed something.. but bit shifting can be done with the power() function.. e.g. 100 left shift 3 and right shift 3

select 100 * power(2,3), convert(int, 100 / power(2,3))

re: Bitmask Handling, part 4: Left-shift and right-shift

Justin Dearing — Sun, 01 Aug 2010 02:26:54 GMT

Stephen,

Yes you can. and I did that to do byte shifting like so:

SELECT

CAST(0xFF * POWER(CAST(256 AS BIGINT), 0) AS BINARY(12)) AS Shift0,

CAST(0xFF * POWER(CAST(256 AS BIGINT), 1) AS BINARY(12)) AS Shift1,

CAST(0xFF * POWER(CAST(256 AS BIGINT), 2) AS BINARY(12)) AS Shift2,

CAST(0xFF * POWER(CAST(256 AS BIGINT), 3) AS BINARY(12)) AS Shift3,

CAST(0xFF * POWER(CAST(256 AS BIGINT), 4) AS BINARY(12)) AS Shift4,

CAST(0xFF * POWER(CAST(256 AS BIGINT), 5) AS BINARY(12)) AS Shift5

re: Bitmask Handling, part 4: Left-shift and right-shift

Adam Machanic — Sun, 01 Aug 2010 19:01:31 GMT

Stephen and Justin:

Yes, that will work, but since we lack unsigned types in T-SQL you can wind up with an overflow exception if you do it like that. Anyway, these techniques are way outdated today thanks to the inclusion of SQLCLR in SQL Server 2005/2008--I certainly don't recommend actually doing this stuff for production purposes :-)