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  • SQL LEFT JOIN help

    - by Stolz
    My scenario: There are 3 tables for storing tv show information; season, episode and episode_translation. My data: There are 3 seasons, with 3 episodes each one, but there is only translation for one episode. My objetive: I want to get a list of all the seasons and episodes for a show. If there is a translation available in a specified language, show it, otherwise show null. My attempt to get serie 1 information in language 1: SELECT season_number AS season,number AS episode,name FROM season NATURAL JOIN episode NATURAL LEFT JOIN episode_trans WHERE id_serie=1 AND id_lang=1 ORDER BY season_number,number result: +--------+---------+--------------------------------+ | season | episode | name | +--------+---------+--------------------------------+ | 3 | 3 | Episode translated into lang 1 | +--------+---------+--------------------------------+ expected result +-----------------+--------------------------------+ | season | episode| name | +-----------------+--------------------------------+ | 1 | 1 | NULL | | 1 | 2 | NULL | | 1 | 3 | NULL | | 2 | 1 | NULL | | 2 | 2 | NULL | | 2 | 3 | NULL | | 3 | 1 | NULL | | 3 | 2 | NULL | | 3 | 3 | Episode translated into lang 1 | +--------+--------+--------------------------------+ Full DB dump http://pastebin.com/Y8yXNHrH

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  • MySQL join headaches, please help!

    - by Andrew Heath
    Ok, I've hit the wall here and need some help. Sample tables are as follows: SCENARIO_NATIONS [scenID] [side] [nation] scen001 1 Germany scen001 2 Britain scen001 2 Canada SCENARIO_NEEDUNITS [scenID] [unitID] scen001 0001 scen001 0003 scen001 0107 scen001 0258 scen001 0759 UNIT_BASIC_DATA [unitID] [nation] [name] 0001 Germany Mortars 0003 Germany Infantry 0107 Britain Lt 0258 Britain Infantry 0759 Canada Kilted Yaksmen Goal: given a scenID, pull a list of units from the database sorted by side, nation, name. I can do everything except for the side inclusion with: SELECT scenario_needunits.scenID, unit_basic_data.nation, unit_basic_data.name FROM scenario_needunits LEFT OUTER JOIN unit_basic_data ON scenario_needunits.unitID=unit_basic_data.unitID WHERE scenario_needunits.scenID='scen001' ORDER BY unit_basic_data.nation ASC, unit_basic_data.name ASC I've tried just dropping the SCENARIO_NATIONS table in as a LEFT OUTER JOIN on scenID but what ends up happening is that ALL units come back with a side of 1 because that's always the first side listed for the scenID in the SCENARIO_NATIONS table. Conceptually, what I think needs to happen is SCENARIO_NATIONS must be joined to both the scenID (to restrict it to just that scenario) and to each unit's nation but I don't have any idea how to do that and my Google-fu is inadequate. :-/

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  • MySQL Join issue

    - by mouthpiec
    Hi, I have the following tables: --table sportactivity-- sport_activity_id, home_team_fk, away_team_fk, competition_id_fk, date, time (tuple example) - 1, 33, 41, 5, 2010-04-14, 05:40:00 --table teams-- team_id, team_name (tuple example) - 1, Algeria Now I have the following SQL statment that I use to extract Team A vs Team B SELECT sport_activity_id, T1.team_name AS TeamA, T2.team_name AS TeamB, DATE_FORMAT( DATE, '%d/%m/%Y' ) AS DATE, DATE_FORMAT( TIME, '%H:%i' ) AS TIME FROM sportactivity JOIN teams T1 ON home_team_fk = T1.team_id JOIN teams T2 ON ( away_team_fk = T2.team_id OR away_team_fk = '0' ) WHERE DATE( DATE ) >= CURDATE( ) ORDER BY DATE( DATE ) My problem is that when team B is empty, I am having irrelevant information .... it seems that it is returning all the combinations. I need a query that when team B is equal to 0, (this can occur in my scenario) I get only Team A - Team B (as 0) once.

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  • 2 Select or 1 Join query ?

    - by xRobot
    I have 2 tables: book ( id, title, age ) ---- 100 milions of rows author ( id, book_id, name, born ) ---- 10 millions of rows Now, supposing I have a generic id of a book. I need to print this page: Title: mybook authors: Tom, Graham, Luis, Clarke, George So... what is the best way to do this ? 1) Simple join like this: Select book.title, author.name From book, author WHERE ( author.book_id = book.id ) AND ( book.id = 342 ) 2) For avoid the join, I could make 2 simple query: Select title FROM book WHERE id = 342 Select name FROM author WHERE book_id = 342 What is the most efficient way ?

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  • mysql join with a "bounce" off a third table

    - by Enkay
    I have 3 mysql tables. companies with company_id and company_name products with product_id and company_id names with product_id, product_name and other info about the product I'm trying to output the product_name and the company_name in one query for a given product_id. Basically I need information from the names and companies tables and the link between them is the products table. How do I do a join that needs to "bounce" off a third table? Something like this but this obviously doesn't work : SELECT product_name, company_name FROM names LEFT OUTER JOIN companies ON (names.product_id = products.product_id and products.company_id = companies.company_id) WHERE product_id = '12345' Thanks!

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  • group_concat on an empty join in MySQL

    - by Yossarian
    Hello, I've got the following problem: I have two tables: (simplified) +--------+ +-----------+ | User | | Role | +--------+ +-----------+ | ID<PK> | | ID <PK> | +--------+ | Name | +-----------+ and M:N relationship between them +-------------+ | User_Role | +-------------+ | User<FK> | | Role<FK> | +-------------+ I need to create a view, which selects me: User, and in one column, all of his Roles (this is done by group_concat). I've tried following: SELECT u.*, group_concat(r.Name separator ',') as Roles FROM User u LEFT JOIN User_Role ur ON ur.User=u.ID LEFT JOIN Role r ON ur.Role=r.ID GROUP BY u.ID; However, this works for an user with some defined roles. Users without role aren't returned. How can I modify the statement, to return me User with empty string in Roles column when User doesn't have any Role? Explanation: I'm passing the SQL data directly to a grid, which then formats itself, and it is easier for me to create slow and complicated view, than to format it in my code. I'm using MySQL

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  • Oracle curcular join sometimes give duplicates, but sometimes does not

    - by Kaushik
    By mistake I wrote a query like this: select * from a,b,c where a.col=b.col and b.col2=c.col2 and c.col3=a.col4 So there is a circular join here. Now the thing is sometimes this query returns duplicate result, sometimes it returns unique(correct) results. I am trying to understand why it does not give duplicate results always. Also if circular joins are not allowed, how come Oracle does not throw an error. EDIT: This is the actual query. After reading ti carefully, I am not sure anymore if this is a circular join or not.It does not seem so...but why I get duplicates only sometime? select * from a,b,c,d where a.col=b.col and b.col=c.col and c.col2=d.col2 and d.col2 =a.col2

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  • Broken count(*) after adding LEFT JOIN

    - by Iain Urquhart
    Since adding the LEFT JOIN to the query below, the count(*) has been returning some strange values, it seems to have added the total rows returned in the query to the 'level': SELECT `n`.*, exp_channel_titles.*, round((`n`.`rgt` - `n`.`lft` - 1) / 2, 0) AS childs, count(*) - 1 + (`n`.`lft` > 1) + 1 AS level, ((min(`p`.`rgt`) - `n`.`rgt` - (`n`.`lft` > 1)) / 2) > 0 AS lower, (((`n`.`lft` - max(`p`.`lft`) > 1))) AS upper FROM `exp_node_tree_6` `n` LEFT JOIN `exp_channel_titles` ON (`n`.`entry_id`=`exp_channel_titles`.`entry_id`), `exp_node_tree_6` `p`, `exp_node_tree_6` WHERE `n`.`lft` BETWEEN `p`.`lft` AND `p`.`rgt` AND ( `p`.`node_id` != `n`.`node_id` OR `n`.`lft` = 1 ) GROUP BY `n`.`node_id` ORDER BY `n`.`lft` I'm totally stumped... Thank you!

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  • MySQL Join Comma Separated Field

    - by neeraj
    I have two tables. First Table is a batch table that contain comma separated student id in field "batch" batch -------------- id batch -------------- 1 1,2 2 3,4 Second Table is marks marks ---------------------- id studentid subject marks 1 1 English 50 2 2 English 40 3 3 English 70 4 1 Math 65 5 4 English 66 6 5 English 75 7 2 Math 55 How we can find those students of first batch id =1 who have scored more than 45 marks in English without using sub query. Problem i found to get this done using a single query is that we can not use IN as an association operator in JOIN statement What changes are required in below query to make it work? SELECT * FROM batch INNER JOIN marks ON marks.studentid IN(batch.batch) where batch.id = 1

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  • C# LINQ join With Just One Row

    - by Soo
    I'm trying to make a query that grabs a single row from an SQL database and updates it. TableA AId AValue TableB BId AId BValue Ok, so TableA and TableB are linked by AId. I want to select a row in TableB based on AValue using a join. The following query is what I have and only grabs a value from TableB based on AId, I just don't know how to grab a row from TableB using AValue. I know you would need to use a join, but I'm not sure how to accomplish that. var row = DbObject.TableB.Single(x => x.AId == 1) row.BValue = 1; DbObject.SubmitChanges();

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  • MySQL AND alternative for eatch table in a join

    - by Scott
    I have a simple join in a query however I need to have a condition on both of the tables "confirmed='yes'" but if one of the tables doesn't have any that match the query returns with no rows. Database: .----------parties----------. | id - party_id - confirmed | |---------------------------| | 1 1 yes | | 1 2 no | | 1 3 no | +---------------------------+ .-----------events----------. | id - event_id - confirmed | |---------------------------| | 1 1 no | +---------------------------+ Query: SELECT p.party_id, e.event_id FROM parties p LEFT JOIN events e ON p.id=e.id WHERE p.id = '1' AND p.party_id IN (1,2,3) AND e.event_id IN (1) AND p.confirmed='yes' AND e.confirmed='yes' It returns nothing but I want it to return party_id 1 with a empty event_id. I hope this make sense and I not missing anything, Thanks for your help!

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  • mysql select multiple rows in join

    - by julio
    Hi-- I have a simple mySQL problem-- I have two tables, one is a user's table, and one is a photos table (each user can upload multiple photos). I'd like to write a query to join these tables, so I can pull all photos associated with a user (up to a certain limit). However, when I do something obvious like this: SELECT *.a, *.b FROM user_table a JOIN photos_table b ON a.id = b.userid it returns a.id, a.name, a.email, a.address, b.id, b.userid, b.photo_title, b.location but it only returns a single photo. Is there a way to return something like: a.id, a.name, a.email, a.address, b.id, b.userid, b.photo_title, b.location, b.id2, b.photo_title2, b.location2 etc. . . for a given LIMIT of photos? Thanks for any ideas.

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  • MySQL AND alternative for each table in a join

    - by Scott
    I have a simple join in a query however I need to have a condition on both of the tables "confirmed='yes'" but if one of the tables doesn't have any that match the query returns with no rows. Database: .----------parties----------. | id - party_id - confirmed | |---------------------------| | 1 1 yes | | 1 2 no | | 1 3 no | +---------------------------+ .-----------events----------. | id - event_id - confirmed | |---------------------------| | 1 1 no | +---------------------------+ Query: SELECT p.party_id, e.event_id FROM parties p LEFT JOIN events e ON p.id=e.id WHERE p.id = '1' AND p.party_id IN (1,2,3) AND e.event_id IN (1) AND p.confirmed='yes' AND e.confirmed='yes' It returns nothing but I want it to return party_id 1 with a empty event_id. I hope this make sense and I not missing anything, Thanks for your help!

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  • Proper Imaging Procedures to Restore and Deploy Image with Separate System Reserved Partition

    - by alharaka
    UPDATE: As per my experience here, no one responded. If I do not hear back from TechNet forum members about it, I will post a bounty here, if it makes a difference. I have banged my head against a wall for what seems like all week. I am going to explain my simple procedure, and how none of it, absolutely none, seems to work afterword despite few alternatives and everyone on the internet telling assuming this is how to do it. Diskpart Commands to Create FS Structure REM Select the disk targeted for deployment. REM REM NOTE: Usually disk 0, but drive failure can make it external USB REM media. This will erase the drive regardless! select disk 0 REM Remove previous formatting. clean REM Create System Reserved partition bootloader and files. create partition primary size=100 REM Format the volume format fs=ntfs label="System Reserved" quick override noerr REM Assign the System Reserved partition the D: mount for now assign letter=C REM The main system partition, size not specified to occupy whole drive. create partition primary REM Format the volume format fs=ntfs quick override noerr REM Assign the OS partition the D: mount for now assign letter=D REM Make this the active/bootable partition. sel disk 0 sel partition 1 active REM Close out the diskpart session. exit Now, I thought this was madness, but it turns out the System Reserved partition and standard "System Partition" (C:, commonly both the boot and system volumes where you find the Windows directory AND the bootmgr/ntldr hardware files, this is where Windows 7 diverges) as mounted in the Windows PE session where I run these commands do not matter. See reference here. Since this needs to be BitLocker-ready, enter this crappy System Reserved partition that is separate 100MB of awesome that goes before the regular boot volume. I do this, then I proceed to the next step. Deploy System Reserved and Normal System Images REM C is still the "System Reserved Partition", and the image is just like it sounds. imagex /apply G:\images\systemreserved.wim 1 C: REM D is now what will be the C: system partition on reboot, supposedly. imagex /apply G:\images\testimage.wim 1 D: Reboot the system Now, the images I just captured should look good. This is not even sysprepped, but reapplying the same fscking image I prepared on the same reference workstation hours before. Problem is I get 0xc000000e could not detect the accessible boot device \Windows\system32\winload.exe or different kinds of nonsense revolving around being able to find the boot volume with all the right files. I try different variations of things, now none of them work. I tried repairs with bcdboot, with a fresh System Reserved partition or not, bootrec, and maually editing the damn BCD store with bcdedit. I tried finalizing the above process with and without bootsect /nt60 C: /force. I need to wrap up and automate this procedure. What am I doing wrong that does not make the image happy, but really just miserable.

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  • Ubuntu 11.10 running in windows 7 (wubi) AND on a separate partition

    - by Pareen
    I am in a very strange situation and need some help: I installed Ubuntu 11.10 through Wubi a while back so that I can use it alongside Windows 7. I was running out of space on my disk when trying to install applications. Without understanding how Wubi worked, I partitioned my C drive (creating a new 90 GB partition) in Windows, booted from the Ubuntu 11.10 install/live disk, and used the "something else" option to create a ext4 (setting the mount point to root) and swap space partitions (/sda5 and /sda6). After the install, my computer no longer boots with the previous Wubi menu and is now using the Linux grub. The options I have are /sda2, which boots Windows 7; /sda1, which doesn't do anything and reloads the same menu, and the run Linux options. So I now have Ubuntu running on a separate partition, as well as the original Wubi install. I want to delete the seperate partition and go back to running Ubuntu on Wubi...if I remove the partition will I need the Windows 7 disk to restore the boot loader? I dont have the Windows 7 disk on me so what is the best way to clean this up so I get rid of the seperate partition? -------------------------------------------------UPDATE----------------------------------------------------- ============================================================================================================ thank you so much for your response. Actually, it would be fantastic if I could migrate my Wubi install into the new partition because I had downloaded the AOSP on the Wubi install (as well as other files) and would love to preserve them. If i can do that and work on the new partition with the old files than that would be great, and I can worry about wiping out the partition completely later on i.e. when I have the windows disk or something. Can you tell me how to do this migration?? So when I select the /sda2, it loads up my Windows. If i click on the Linux, it loads up the newly install Linux (my files that were on the Wubi install aren't there) fine. If I click on the /sda1 (SYSTEM_DRIVE... this is what the Wubi was using to boot the menu that let me select Windows 7 or Ubuntu)... it fails and just reloads the original menu. Here is the link to my boot info script http://pastebin.com/dMrY0NL3

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  • Gparted can't create partition table

    - by William
    Here's what the problem is. About a day or so ago I used Gparted live cd to create 3 NTFS primary partitions on my external 500 gig Goflex and one extended with 2 logical partitiones. I had planned to install windows 8 on the first partition, then ubuntu and kubuntu on the other 2. After I finished partitioning my drive with gparted, I booted into windows vista to make my bootable windows 8 usb to install it with, I also decided to check to make sure all my partitions were working properly. Then I found they were, and they weren't. My 50 gig first partition I had planned to install windows on showed up normal and the 300 gigs of space left in the extended partition did as well, the rest showed up as raw. So I figured alright, something went awal while making the partitions, so I booted up gparted once again. Then to my surprise gparted showed the entire drive as unallocated, and when I refreshed the list, it showed as all the partitions I had made earlier, buy with a exclamation mark by them all. So I figured ok, might be a problem with the partition table as I'd seen a similar problem in past on a drive that was not partitioned at all, so I decided to create a new partition table and take the time out again to sit and wait. Then I got a message saying gparted could not create the partition table, followed by it showing the entire drive as formatted into ntfs. After that I figured ok I'll take a break, come back in a hour, maybe it's something I did. So a hour later I came back after having booted up windows, plugged the drive in to see if by some miracle windows could access the drive. In disk management when I plugged the drive in, it would freeze attempting to read the drive, as I'd seen in the past with raw disks, yet when I unplugged it I got a glimpse of disk management showing it as a perfectly fine ntfs file system on the drive followed by a "you must format disk K in order to use it". So I then was assured the disk was raw as that is what had happened in the past, followed by a new partition table through gparted to fix the problem and a 10 hour format in windows. So I once again booted up gparted, to get the message "error fsyncing/closing/dev/sdg:input/output error" followed by "error opening dev/sdg No such file in directory" after I refreshed and somehow saw the disk show up as perfectly fine ntfs and then tried to create a new partition table to try to wipe out all my problems and start over again. And not gparted only shows the drive there about 1/10 refreshes the rest I get the directory error. If anybody can assist me in any way shape or form I will be thankful.

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  • windows partition not booting

    - by bumbling fool
    Using clonezilla, I cloned a win7 installation from the first partition on one drive to the first partition on a second larger drive and then installed ubuntu into the second partition (same configuration as the original drive, just maverick instead of karmic). ubuntu detected the win7 partition properly and added it to the grub menu. However, when I choose the win7 option in grub, I just get a black screen and blinking cursor :( Suggestions please?!?

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  • installation ubunto 14.01 on a different partition with windows 8.1

    - by bilel abidi
    Please assist me. I am eager to install Ubunto 14.01 on a different partition but I do not know how to do it. I have HP with windows 7 pre-installed then I upgraded to windows 8.1 please show me how to make a dedicated partition to install ubuntu 14.01. please find the partition that I have. I appreciate your help on a I have : partition : /dev/sda1 NTFS label system 922.50KB /dev/ sda2 NTFS 199.00MIB flags : boot /dev/sda3 NTFS label receovery 488.77 GB /dev/sda4 unknown 16 GB unallocated 1 MIB

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  • How to resize a LVM partition?

    - by iiddaannyy
    I want to shrink my second (lvm) partition, so I can create a new partition in the freespace. I am using Live-CD to do so, because I know I can't resize/move this partition while it is in use. When I opened GParted in Live-CD, I realized that I could not resize the partition, because when I right-click it, the option "resize/move" is disabled. I tried to unmount it, to "lazy" unmount it (umount -l /dev/sda2) but it didn't work. A screenshot from GParted:

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  • how to display list of partition under 'Go' menu

    - by Roy
    I'm installing ubuntu 12.04 on my asus A43S notebook, but couldn't see any other partition under the 'Go' menu. I tried 'sudo fdisk -l' seems fine, it displays all partition. I also installed ubuntu 12.04 on my PC but there were no problems, all partition are listed under the 'Go' menu, and automaticly mounted when I clicked on them. question is, how to display all partition just like on my PC does, I don't want to mount via terminal each time I need to access them. thanks.

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  • Weird Ubuntu Desktop Boot Partition On External Hard Drive

    - by Magnitus
    I have a Thinkpad with Windows 7. Last time I installed an Ubuntu/Windows dual boot, Windows was never same after and regularly got corrupted so this time, I installed Ubuntu on a separate external hard drive. I took a 500 GB external hard drive and used Windows to shrink the partition on it to 400 GB, freeing 100 GB to install Ubuntu. Then I modified the booting priority of my computer to boot from the external hard drive if present. Then, I installed Ubuntu desktop on the external hard drive using a DVD, picked the most simplistic partitioning scheme I could get away with (didn't go auto as it didn't include the external hard drive as a choice) and voilà. Fast forward some time and I'm trying to refresh my understanding of Linux partitions to install a bunch of servers, so I'm looking at the current partitioning scheme on my external hard drive and find the boot partition puzzling... sda is my integrated hard drive with Windows 7. sdb is my Ubuntu desktop external hard drive. Running parted on sdb, I get this: (parted) print Model: WD My Passport 0740 (scsi) Disk /dev/sdb: 500GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 1049kB 393GB 393GB primary ntfs boot 2 393GB 500GB 107GB extended 5 393GB 425GB 32.8GB logical linux-swap(v1) 6 425GB 500GB 74.6GB logical ext4 At this point, I'm wondering why the ntfs partition is flagged as "boot" and not my ext4 partition which is the partition that contains / (and by extension, /boot since it's not on its own separate partition). Looking at mtab only confirms what I already know: eric@eric-ThinkPad-W530:~$ sudo cat /etc/mtab /dev/sdb6 / ext4 rw,errors=remount-ro 0 0 proc /proc proc rw,noexec,nosuid,nodev 0 0 sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0 none /sys/fs/cgroup tmpfs rw 0 0 none /sys/fs/fuse/connections fusectl rw 0 0 none /sys/kernel/debug debugfs rw 0 0 none /sys/kernel/security securityfs rw 0 0 udev /dev devtmpfs rw,mode=0755 0 0 devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0 tmpfs /run tmpfs rw,noexec,nosuid,size=10%,mode=0755 0 0 none /run/lock tmpfs rw,noexec,nosuid,nodev,size=5242880 0 0 none /run/shm tmpfs rw,nosuid,nodev 0 0 none /run/user tmpfs rw,noexec,nosuid,nodev,size=104857600,mode=0755 0 0 none /sys/fs/pstore pstore rw 0 0 systemd /sys/fs/cgroup/systemd cgroup rw,noexec,nosuid,nodev,none,name=systemd 0 0 gvfsd-fuse /run/user/1000/gvfs fuse.gvfsd-fuse rw,nosuid,nodev,user=eric 0 0 /dev/sdb1 /media/eric/My\040Passport fuseblk rw,nosuid,nodev,allow_other,default_permissions,blksize=4096 0 0 My lack of understanding concerning this is not vital to anything (this is only my development desktop partition), but somehow annoys me. Any insight that could shed some light on this would be welcome.

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  • how to disable luks partition from showing up in nautlus panel

    - by yemu
    I have a luks setup with encrypted partition. And I don't want everyone on my computer to see that I have such partition. Unfortunately it shows up in the nautilus "devices" panel as "Encrypted partition". Is there a way to prevent it from showing there? I plan to setup authentication with a keyfile on usb, but for now I can live without the gnome authentication dialog, and open and mount the partition from command line.

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  • Join and sum not compatible matrices through data.table

    - by leodido
    My goal is to "sum" two not compatible matrices (matrices with different dimensions) using (and preserving) row and column names. I've figured this approach: convert the matrices to data.table objects, join them and then sum columns vectors. An example: > M1 1 3 4 5 7 8 1 0 0 1 0 0 0 3 0 0 0 0 0 0 4 1 0 0 0 0 0 5 0 0 0 0 0 0 7 0 0 0 0 1 0 8 0 0 0 0 0 0 > M2 1 3 4 5 8 1 0 0 1 0 0 3 0 0 0 0 0 4 1 0 0 0 0 5 0 0 0 0 0 8 0 0 0 0 0 > M1 %ms% M2 1 3 4 5 7 8 1 0 0 2 0 0 0 3 0 0 0 0 0 0 4 2 0 0 0 0 0 5 0 0 0 0 0 0 7 0 0 0 0 1 0 8 0 0 0 0 0 0 This is my code: M1 <- matrix(c(0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0), byrow = TRUE, ncol = 6) colnames(M1) <- c(1,3,4,5,7,8) M2 <- matrix(c(0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0), byrow = TRUE, ncol = 5) colnames(M2) <- c(1,3,4,5,8) # to data.table objects DT1 <- data.table(M1, keep.rownames = TRUE, key = "rn") DT2 <- data.table(M2, keep.rownames = TRUE, key = "rn") # join and sum of common columns if (nrow(DT1) > nrow(DT2)) { A <- DT2[DT1, roll = TRUE] A[, list(X1 = X1 + X1.1, X3 = X3 + X3.1, X4 = X4 + X4.1, X5 = X5 + X5.1, X7, X8 = X8 + X8.1), by = rn] } That outputs: rn X1 X3 X4 X5 X7 X8 1: 1 0 0 2 0 0 0 2: 3 0 0 0 0 0 0 3: 4 2 0 0 0 0 0 4: 5 0 0 0 0 0 0 5: 7 0 0 0 0 1 0 6: 8 0 0 0 0 0 0 Then I can convert back this data.table to a matrix and fix row and column names. The questions are: how to generalize this procedure? I need a way to automatically create list(X1 = X1 + X1.1, X3 = X3 + X3.1, X4 = X4 + X4.1, X5 = X5 + X5.1, X7, X8 = X8 + X8.1) because i want to apply this function to matrices which dimensions (and row/columns names) are not known in advance. In summary I need a merge procedure that behaves as described. there are other strategies/implementations that achieve the same goal that are, at the same time, faster and generalized? (hoping that some data.table monster help me) to what kind of join (inner, outer, etc. etc.) is assimilable this procedure? Thanks in advance. p.s.: I'm using data.table version 1.8.2 EDIT - SOLUTIONS @Aaron solution. No external libraries, only base R. It works also on list of matrices. add_matrices_1 <- function(...) { a <- list(...) cols <- sort(unique(unlist(lapply(a, colnames)))) rows <- sort(unique(unlist(lapply(a, rownames)))) out <- array(0, dim = c(length(rows), length(cols)), dimnames = list(rows,cols)) for (m in a) out[rownames(m), colnames(m)] <- out[rownames(m), colnames(m)] + m out } @MadScone solution. Used reshape2 package. It works only on two matrices per call. add_matrices_2 <- function(m1, m2) { m <- acast(rbind(melt(M1), melt(M2)), Var1~Var2, fun.aggregate = sum) mn <- unique(colnames(m1), colnames(m2)) rownames(m) <- mn colnames(m) <- mn m } BENCHMARK (100 runs with microbenchmark package) Unit: microseconds expr min lq median uq max 1 add_matrices_1 196.009 257.5865 282.027 291.2735 549.397 2 add_matrices_2 13737.851 14697.9790 14864.778 16285.7650 25567.448 No need to comment the benchmark: @Aaron solution wins. I'll continue to investigate a similar solution for data.table objects. I'll add other solutions eventually reported or discovered.

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  • How do I boot to the Recovery Partition on an eMachines D620 notebook?

    - by GraemeF
    I installed the Windows 7 RC on my wife's laptop and now need to reinstall Vista for her. I was very careful to leave the recovery partition intact so that I could do this, but I don't see a way to boot to it. In the Disk Management console I can see the "9.77GB Healthy (Recovery Partition)" partition but I can't do anything with it - the context menu only contains the Help option. Any ideas?

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  • Shrink system volume, create new partition, & enlarge current partitions w/o losing data?

    - by studiohack
    My machine has a 300 GB hard drive. I'm planning to reinstall Windows 7 on this machine soon. It has three partitions: a System partition, and two equal data partitions for particular types of data (music, photos, docs, etc). These data partitions are too small for the data they hold, and the system partition is large enough to be shrunk. I want to create four partitions in preparation for the fresh reinstall, a System partition, and three data partitions of varying sizes (40, 50, & 60 GB respectively). My question: Can I shrink the System volume, create another partition, and make the existing two data partitions bigger without losing any data that is currently on the hard drive? Or is it better to format the whole thing, and create partitions after (thus removing the current OS) with a partitioning tool booting from CD? Can I reformat and create partitions with the Windows 7 set up DVD?

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