User Comments
| Posted by greg gerard on October 25 2005 12:44pm | [Delete] [Edit] |
That is an sample of utilisation:
SELECT
SUM(IF(rubrik & 1, 1, 0)) actus,
SUM(IF(rubrik & 2, 1, 0)) shopping,
SUM(IF(rubrik & 4, 1, 0)) utils,
SUM(IF(rubrik & 8, 1, 0)) communication,
SUM(IF(rubrik & 16, 1, 0)) services,
COUNT(user_id) AS total,
FROM preferences p
Where rubrik is an integer.
| Posted by Neil Davis on April 3 2008 8:07pm | [Delete] [Edit] |
If you store your ip addresses as a 32 bit unsigned integer representation instead of strings(using INET_ATON()), you can use bitwise operators to pull the octets for grouping and sorting when you need to retrieve them:
select
ipAddress,
(ipAddress >> 24) as firstOctet,
(ipAddress>>16<<16)-(ipAddress>>24<<24)>>16 as secondOctet,
(ipAddress>>8<<8)-(ipAddress>>16<<16)>>8 as thirdOctet,
ipAddress-(ipAddress>>8<<8) as fourthOctet
from ips;
Result:
+------------+------------+-------------+------------+-------------+
| ipAddress | firstOctet | secondOctet | thirdOctet | fourthOctet |
+------------+------------+-------------+------------+-------------+
| 2082027709 | 124 | 25 | 56 | 189 |
| 2082027710 | 124 | 25 | 56 | 190 |
| 2082027711 | 124 | 25 | 56 | 191 |
| 2082093145 | 124 | 26 | 56 | 89 |
| 2082093146 | 124 | 26 | 56 | 90 |
+------------+------------+-------------+------------+-------------+
This way you don't need a string parser to separate the octets for display, drill down menus, sorting etc, and don't need to tear the octets apart with a string parser to put them in separate fields.
If these are your IP addresses I sincerely apologize. I just pulled them out of thin air to write this sql :D
There are 10 types of people in the world...
Sorry had to throw that in there 8)
There are probably "easier" ways to do this, but they aren't as efficient. I had a requirement for a tree view of ip addresses and this seems to be the easiest way to do it.
-Neil
| Posted by Phillip Temple on September 11 2008 1:32pm | [Delete] [Edit] |
Neil, you will find the following more efficient:
ipAddress, (ipAddress >> 24) as firstOctet,
(ipAddress>>16) & 255 as secondOctet,
(ipAddress>>8) & 255 as thirdOctet,
ipAddress & 255 as fourthOctet
from ips;
Phillip.
| Posted by Ben Wiseley on August 7 2009 9:54pm | [Delete] [Edit] |
This took me a while to figure out so, if it helps anyone...
If you want to turn on/off bit settings you do it like so, you need to do the &~ first and the | second.
Say prefs = 1636 (1024 | 512 | 64 | 32 | 4) and you want to turn off 512 and 64 and turn on 4 and not touch 1024
select prefs &~ 512 &~ 64 | 4;
1060
Even if prefs is 0 - you get the same result
Just make sure to put all the &~s first
| Posted by Will Entriken on December 11 2009 2:56pm | [Delete] [Edit] |
@ greg gerard
In your case, could use SIGN() rather than IF. Or given that you are using SUM(), even could use >>:
SELECT
SUM(rubrik & 1) actus,
SUM(rubrik & 2)>>1 shopping,
SUM(rubrik & 4)>>2 utils,
SUM(rubrik & 8)>>3 communication,
SUM(rubrik & 16)>>4 services,
COUNT(user_id) AS total,
FROM preferences p
| Posted by Mark Cain on December 29 2009 3:08am | [Delete] [Edit] |
Seems there is a shortage of examples for bitwise logic in MySQL. Here is how I have used it:
I have a database of customers who buy services from a company. The status of the customer tells me what service(s) they use and if they are current in buying that service. So for an example lets say my services include:
Pool Service, lawn mowing, window washing, tree trimming, house painting, mobile oil change, etc.. (you get the idea).
I set a number scheme for the status such as:
1 = Prospective Customer
2 = Cancelled Service
4 = Pool Service
8 = lawn mowing
16 = window washing
32 = tree trimming
64 = house painting
128 = mobile oil change
With this scheme a customer who needs pool service (4) and window washing (16) will have a status of 20 (4 + 16). A prospect (1) who might be interested in a mobile oil change (128) would have a status of 129 (1+128). etc...
Bitwise logic allows me to select customers who buy particular services based on their status value.
SELECT * FROM customers WHERE status & 1
//returns all prospects)
SELECT * FROM customers WHERE status & 16
//returns all of my window washing customers even if they are cancelled
SELECT * FROM customers WHERE (status & 16) AND !(status & 2)
//returns all of my window washing customers but not the cancelled ones
SELECT * FROM customers WHERE status & 36
//returns all of my tree trimming AND pool service customers i.e. 32+4
SELECT * FROM customers WHERE status & 10
//returns all cancelled lawn moving customers i.e. 2+8
SELECT * FROM customers WHERE (status & 32) AND !(status & 128)
//returns all tree trimming customers who do not get a mobile oil change
| Posted by Chris Wagner on May 28 2011 2:30am | [Delete] [Edit] |
@Mark Cain.
What u just described is a reroll of FIND_IN_SET and ENUM.
