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  • Meaning of Primary Key to Microsoft SQL Server 2008

    - by usr
    What meaning does the concept of a primary key have to the database engine of SQL Server? I don't mean the clustered/nonclustered index created on the "ID" column, i mean the constraint object "primary key". Does it matter if it exists or not? Alternatives: alter table add primary key clustered alter table create clustered index Does it make a difference?

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  • Are GUID primary keys bad in theory, or just practice?

    - by Yarin
    Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice?

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  • The Next-gen Databases

    - by Randin
    I'm learning traditional Relational Databases (with PostgreSQL) and doing some research I've come across some new types of databases. CouchDB, Drizzle, and Scalaris to name a few, what is going to be the next database technologies to deal with?

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  • What are the reasons *not* to use a GUID for a primary key?

    - by Yarin
    Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice?

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  • Recommended book for Sql Server query optimisation

    - by Patrick Honorez
    Even if I have made a certification exam on Sql Server Design and implementation , I have no clue about how to trace/debug/optimise performance in Sql Sever. Now the database I built is really business critical, and getting big, so it is time for me to dig into optimisation, specially regarding when/where to add indexes. Can you recommend a good book on this subject ? (smaller is better :) Just in case: I am using Sql Server 2008. Thanks

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  • What's wrong with foreign keys?

    - by kronoz
    I remember hearing Joel mention in the podcast that he'd barely ever used a foreign key (if I remember correctly). However, to me they seem pretty vital to avoid duplication and subsequent data integrity problems throughout your database. Do people have some solid reasons as to why (to avoid a discussion in lines with SO principals)? Edit: "I've yet to have a reason to create a foreign key, so this might be my first reason to actually set up one."

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  • Object Oriented vs Relational Databases

    - by Dan
    Objects oriented databases seem like a really cool idea to me, no need to worry about mapping your domain model to your database model, no messing around with sql or ORM tools. The way I understand it, relational DBs offer some advantages when there is massive amounts of data, and searching an indexing need to be done. To my mind 99% of websites are not massive, and enterprise issues never need to be thought about, so why arn't OO DBs more widely used?

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  • How do I update the members of a MySQL SET Type?

    - by MachinationX
    I have a table of values, with one of the columns being of type SET. If it currently has the members ('a', 'b', 'c', 'd'), how do I add 'e' to the possible values? I realize that using a SET type is a little strange, and I'm unclear why one would use it instead of a foreign key to another table with the values of the set, but I didn't design the database in question, and can't change it that much. Thanks for your help!

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  • methods of joining 2 tables without using JOIN or SELECT more than one distinct table in the query

    - by GB_J
    Is there a way of joining results from 2 tables without using JOIN or SELECT from more than one table? The reason being the database im working with requires queries that only contain SELECT, FROM, and WHERE clauses containing only one distinct table. I do, however, need information from other tables for the project i'm working on. More info: the querier returns the query results in a .csv format, is there something we can manipulate there?

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  • Oracle/SQL table attribute question

    - by UnceRawr
    I have been given a context schema for a database i need to make for my coursework but some of the attributes (column names) contain letters in brackets at the end of them such as: *x_Number (Adm) *x_Number (A) *x_Number (P) The problem is i have no idea what these letters mean! Can anyone help?

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  • Q&A: Oracle's Paul Needham on How to Defend Against Insider Attacks

    - by Troy Kitch
    Source: Database Insider Newsletter: The threat from insider attacks continues to grow. In fact, just since January 1, 2014, insider breaches have been reported by a major consumer bank, a major healthcare organization, and a range of state and local agencies, according to the Privacy Rights Clearinghouse.  We asked Paul Needham, Oracle senior director, product management, to shed light on the nature of these pernicious risks—and how organizations can best defend themselves against the threat from insider risks. Q. First, can you please define the term "insider" in this context? A. According to the CERT Insider Threat Center, a malicious insider is a current or former employee, contractor, or business partner who "has or had authorized access to an organization's network, system, or data and intentionally exceeded or misused that access in a manner that negatively affected the confidentiality, integrity, or availability of the organization's information or information systems."  Q. What has changed with regard to insider risks? A. We are actually seeing the risk of privileged insiders growing. In the latest Independent Oracle Users Group Data Security Survey, the number of organizations that had not taken steps to prevent privileged user access to sensitive information had grown from 37 percent to 42 percent. Additionally, 63 percent of respondents say that insider attacks represent a medium-to-high risk—higher than any other category except human error (by an insider, I might add). Q. What are the dangers of this type of risk? A. Insiders tend to have special insight and access into the kinds of data that are especially sensitive. Breaches can result in long-term legal issues and financial penalties. They can also damage an organization's brand in a way that directly impacts its bottom line. Finally, there is the potential loss of intellectual property, which can have serious long-term consequences because of the loss of market advantage.  Q. How can organizations protect themselves against abuse of privileged access? A. Every organization has privileged users and that will always be the case. The questions are how much access should those users have to application data stored in the database, and how can that default access be controlled? Oracle Database Vault (See image) was designed specifically for this purpose and helps protect application data against unauthorized access.  Oracle Database Vault can be used to block default privileged user access from inside the database, as well as increase security controls on the application itself. Attacks can and do come from inside the organization, and they are just as likely to come from outside as attempts to exploit a privileged account.  Using Oracle Database Vault protection, boundaries can be placed around database schemas, objects, and roles, preventing privileged account access from being exploited by hackers and insiders.  A new Oracle Database Vault capability called privilege analysis identifies privileges and roles used at runtime, which can then be audited or revoked by the security administrators to reduce the attack surface and increase the security of applications overall.  For a more comprehensive look at controlling data access and restricting privileged data in Oracle Database, download Needham's new e-book, Securing Oracle Database 12c: A Technical Primer. 

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  • Oracle Data Integration Solutions and the Oracle EXADATA Database Machine

    - by João Vilanova
    Oracle's data integration solutions provide a complete, open and integrated solution for building, deploying, and managing real-time data-centric architectures in operational and analytical environments. Fully integrated with and optimized for the Oracle Exadata Database Machine, Oracle's data integration solutions take data integration to the next level and delivers extremeperformance and scalability for all the enterprise data movement and transformation needs. Easy-to-use, open and standards-based Oracle's data integration solutions dramatically improve productivity, provide unparalleled efficiency, and lower the cost of ownership.You can watch a video about this subject, after clicking on the link below.DIS for EXADATA Video

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  • finite state machine used in mario like platform game

    - by juakob
    I dont understand how to use a finite state machine with the entity controlled by the player. For example i have a mario(2d platform) i can jump,run,walk,take damage,swim,etc so my first thought was to use this actions as states. But what happen when you are running when you take damage? or jumping taking damage and shooting at the same time? I just want to add functionalities(actions) to the player in a clean way(not using ifs for all the actions in the entity update)

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  • Using ext4 in VMware machine

    First of all, using a journaling filesystems like NTFS, ext4, XFS, or JFS (not to name all of them) is a very good idea and nowadays unthinkable not to do. Linux offers a good variety of different option as journaling filesystem for your system. Since years I am using SGI's XFS and I am pretty confident with stability, performance and liability of the system. In earlier years I had to struggle with incompatibilities between XFS and the boot loader. Using an ext2 formatted /boot solved this issue. But, wow, that is ages ago! Lately, I had to setup a fresh Lucid Lynx (Ubuntu 10.04 LTS) system for a change of our internal groupware / messaging system. Therefore, I fired up a new virtual machine with almost standard configuration in VMware Server and run through our network-based PXE boot and installation procedure. At a certain step in this process, Ubuntu asks you about the partitioning of your hard drive(s). Honestly, I have to say that only out of curiousity I sticked to the "default" suggestion and gave my faith and trust into the Ubuntu installation routine... Resulting to have an ext4 based root mount point ( / ). The rest of the installation went on without further concerns or worries. Note:I really can't remember why I chose to go away from my favourite... Well, it should turn out to be the wrong decision after all. Ok, let's continue the story about ext4 in a VMware based virtual machine. After some hours installing additional packages and configuring the new system using LDAP for general authentication and login, I had an "out-of-the-box" usable enterprise messaging system based on Zarafa 6.40 Community Edition inclusive proper SSL-based Webaccess interface and Z-Push extension for ActiveSync with my Nokia mobile. Straightforward and pretty nice for the time spent on the setup. Having priority on other tasks I let the system just running and didn't pay any further attention at all. Until I run into an upgrade of "Mail for Exchange" on Symbian OS. My mobile did not bother me at all with the upgrade and everything went smooth, but trying to re-establish the ActiveSync connection to the Zarafa messaging system resulted in a frustating situation. So, I shifted my focus back to the Linux system and I was amazed to figure out that the root had been remounted readonly due to hard drive failures or at least ext4 reported errors. Firing up Google only confirmed my concerns and it seems that using ext4 for VMware based virtual machines does not look like a stable and reliable candidate to me. You might consider reading those external resources: ext4 fs corruption under VMWare Server 2.01Bug #389555 - ext4 filesystem corruption Well, I learned my lesson and ext{2|3|4} based filesystems are not going to be used on any of my Linux systems or customer installations in the future. Addendum: I did not try this setup in other virtualization environments like VirtualBox, qemu, kvm, Xen, etc.

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  • Virtual Machine Storage Provisioning and best practises

    If you're using Virtualization technology, then at some point you'll have run out of (or will run out of) virtual disk space, & had to provision extra storage; are you confident that you know how to do that? Sean Duffy makes sure you're doing it right, sharing his recommendations and tips in this step-by-step guide to Virtual Machine Storage provisioning for VMware. Follow this advice, and you'll be a Virtualization Veteran in no time.

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  • Programming Language, Turing Completeness and Turing Machine

    - by Amumu
    A programming language is said to be Turing Completeness if it can successfully simulate a universal TM. Let's take functional programming language for example. In functional programming, function has highest priority over anything. You can pass functions around like any primitives or objects. This is called first class function. In functional programming, your function does not produce side effect i.e. output strings onto screen, change the state of variables outside of its scope. Each function has a copy of its own objects if the objects are passed from the outside, and the copied objects are returned once the function finishes its job. Each function written purely in functional style is completely independent to anything outside of it. Thus, the complexity of the overall system is reduced. This is referred as referential transparency. In functional programming, each function can have its local variables kept its values even after the function exits. This is done by the garbage collector. The value can be reused the next time the function is called again. This is called memoization. A function usually should solve only one thing. It should model only one algorithm to answer a problem. Do you think that a function in a functional language with above properties simulate a Turing Machines? Functions (= algorithms = Turing Machines) are able to be passed around as input and returned as output. TM also accepts and simulate other TMs Memoization models the set of states of a Turing Machine. The memorized variables can be used to determine states of a TM (i.e. which lines to execute, what behavior should it take in a give state ...). Also, you can use memoization to simulate your internal tape storage. In language like C/C++, when a function exits, you lose all of its internal data (unless you store it elsewhere outside of its scope). The set of symbols are the set of all strings in a programming language, which is the higher level and human-readable version of machine code (opcode) Start state is the beginning of the function. However, with memoization, start state can be determined by memoization or if you want, switch/if-else statement in imperative programming language. But then, you can't Final accepting state when the function returns a value, or rejects if an exception happens. Thus, the function (= algorithm = TM) is decidable. Otherwise, it's undecidable. I'm not sure about this. What do you think? Is my thinking true on all of this? The reason I bring function in functional programming because I think it's closer to the idea of TM. What experience with other programming languages do you have which make you feel the idea of TM and the ideas of Computer Science in general? Can you specify how you think?

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  • Best way to remote restart Ubuntu from Windows machine

    - by robsoft
    Background: I'm looking to put a series of Ubuntu machines into retail locations, they're being used as dumb kiosks to show a series of slides onto large LCD panel TV screens. Once installed, they won't have a keyboard or mouse connected but will have a fixed IP on the local network. Everything is configured to auto-start, no automatic updates, no power saving etc - I think we're pretty-much good to go apart from one thing. I need the retail staff to be able to restart the boxes if a problem arises. We have VNC running (now that we've turned off desktop enhancements!) so that we can remotely get into the machines if we need to, but that's not something we would allow the retail staff to do. The machines are going to be physically 'out of the way' (probably in the ceiling space) so the power button is not easily accessible!. I'd like to have some means of allowing the retail staff to restart the Ubuntu machine, from the desktop of one of their Windows terminals. I don't really want to give them some kind of raw terminal access (the command line will frighten them!) and I don't want them to use VNC (as stated above). Ideally there would be an icon on the Windows desktop, they double-click it, reply to a simple 'are you sure?' prompt, and then the Ubuntu box is told to restart. The Windows side of that won't be a problem, we can write something using Delphi, Python & Qt4, whatever - it's the Ubuntu side of it I'm stuck with. Out of sight/view, could I have a Windows program open a terminal across the network and tell Ubuntu to restart? Is this what SSH could be used for (I have never set that kind of thing up). The Windows programming side isn't really an issue, it's just that I'm a total Ubuntu noob and don't know where to start from the platform point of view. The other thing we considered is also having the machine automatically restart itself at a set time each day (obviously out of store hours!). To me, that seems a bit unnecessary (though forcing a restart once a week/month might be worthwhile). Any thoughts or suggestions? Being able to restart the box on demand across the network is my prime requirement.

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  • Duplicate ping response when running Ubuntu as virtual machine (VMWare)

    - by Stonerain
    I have the following setup: My router - 192.168.0.1 My host computer (Windows 7) - 192.168.0.3 And Ubuntu is running as virtual machine on the host. VMWare network settings is Bridged mode. I've modified Ubuntu network settings in /etc/netowrk/interfaces, set the following config: iface eth0 inet static address 192.168.0.220 netmask 255.255.255.0 network 192.168.0.0 broadcast 192.168.0.255 gateway 192.168.0.1 Internet works correctly, I can install packages. But it gets weird if I try to ping something I get this: PING belpak.by (193.232.248.80) 56(84) bytes of data. From 192.168.0.1 icmp_seq=1 Time to live exceeded From 192.168.0.1 icmp_seq=1 Time to live exceeded From 192.168.0.1 icmp_seq=1 Time to live exceeded From 192.168.0.1 icmp_seq=1 Time to live exceeded From 192.168.0.1 icmp_seq=1 Time to live exceeded 64 bytes from belhost.by (193.232.248.80): icmp_seq=1 ttl=250 time=17.0 ms 64 bytes from belhost.by (193.232.248.80): icmp_seq=1 ttl=249 time=17.0 ms (DUP! ) 64 bytes from belhost.by (193.232.248.80): icmp_seq=1 ttl=248 time=17.0 ms (DUP! ) 64 bytes from belhost.by (193.232.248.80): icmp_seq=1 ttl=247 time=17.0 ms (DUP! ) 64 bytes from belhost.by (193.232.248.80): icmp_seq=1 ttl=246 time=17.0 ms (DUP! ) ^CFrom 192.168.0.1 icmp_seq=2 Time to live exceeded --- belpak.by ping statistics --- 2 packets transmitted, 1 received, +4 duplicates, +6 errors, 50% packet loss, ti me 999ms rtt min/avg/max/mdev = 17.023/17.041/17.048/0.117 ms I think even more interesting are the results of pinging the router itself: stonerain@ubuntu:~$ ping 192.168.0.1 -c 1 PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data. From 192.168.0.3: icmp_seq=1 Redirect Network(New nexthop: 192.168.0.1) 64 bytes from 192.168.0.1: icmp_seq=1 ttl=254 time=6.64 ms --- 192.168.0.1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 6.644/6.644/6.644/0.000 ms But if I set -c 2: ... 64 bytes from 192.168.0.1: icmp_seq=1 ttl=252 time=13.5 ms (DUP!) 64 bytes from 192.168.0.1: icmp_seq=1 ttl=251 time=13.5 ms (DUP!) 64 bytes from 192.168.0.1: icmp_seq=1 ttl=254 time=13.5 ms (DUP!) 64 bytes from 192.168.0.1: icmp_seq=1 ttl=253 time=13.5 ms (DUP!) 64 bytes from 192.168.0.1: icmp_seq=1 ttl=252 time=13.5 ms (DUP!) 64 bytes from 192.168.0.1: icmp_seq=1 ttl=251 time=13.5 ms (DUP!) From 192.168.0.3: icmp_seq=2 Redirect Network(New nexthop: 192.168.0.1) 64 bytes from 192.168.0.1: icmp_seq=2 ttl=254 time=7.87 ms --- 192.168.0.1 ping statistics --- 2 packets transmitted, 2 received, +256 duplicates, 0% packet loss, time 1002ms rtt min/avg/max/mdev = 6.666/10.141/13.556/2.410 ms Pinging host machine on the other hand works absolutely correctly: no DUPs, no errors. What seems to be the problem and how can I fix it? Thank you.

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  • Remote Desktop from a ubuntu 13.04 to an Ubuntu 13.04 machine so the user on the second machine can see my movments

    - by user163169
    I would like to remote desktop/VPN from an Ubuntu 13.04 computer (a) to an Ubuntu 13.04 computer(b) so the user(s) on the second machine can see my movements. I would like something a lot like team-viewer or Join.me but these machines do not have Internet but that are attached on a local network and I can VPN to them but that can not see what I am doing and I need them to be able to see my movements.

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  • NFS (with Kerberos) mount failing due to "Server not found in Kerberos database" error

    - by Kendall Hopkins
    When running: `sudo mount -t nfs4 -o sec=krb5 sol.domain.com:/ /mnt` I get this error on the client: mount.nfs4: access denied by server while mounting sol.domain.com:/ And on the server syslogs UNKNOWN_SERVER: authtime 0, nfs/[email protected] for nfs/ip-#-#-#-#[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for nfs/ip-#-#-#-#[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database UNKNOWN_SERVER: authtime 0, nfs/[email protected] for krbtgt/[email protected], Server not found in Kerberos database Server keytab file: ubuntu@sol:~$ sudo klist -e -k /etc/krb5.keytab Keytab name: WRFILE:/etc/krb5.keytab KVNO Principal ---- -------------------------------------------------------------------------- 7 host/[email protected] (aes256-cts-hmac-sha1-96) 7 host/[email protected] (arcfour-hmac) 7 host/[email protected] (des3-cbc-sha1) 7 host/[email protected] (des-cbc-crc) 9 nfs/[email protected] (aes256-cts-hmac-sha1-96) 9 nfs/[email protected] (arcfour-hmac) 9 nfs/[email protected] (des3-cbc-sha1) 9 nfs/[email protected] (des-cbc-crc) Client keytab file: ubuntu@mercury:~$ sudo klist -e -k /etc/krb5.keytab Keytab name: WRFILE:/etc/krb5.keytab KVNO Principal ---- -------------------------------------------------------------------------- 3 host/[email protected] (aes256-cts-hmac-sha1-96) 3 host/[email protected] (arcfour-hmac) 3 host/[email protected] (des3-cbc-sha1) 3 host/[email protected] (des-cbc-crc) 3 nfs/[email protected] (aes256-cts-hmac-sha1-96) 3 nfs/[email protected] (arcfour-hmac) 3 nfs/[email protected] (des3-cbc-sha1) 3 nfs/[email protected] (des-cbc-crc)

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  • How to transfer Windows Vista disk image to new machine

    - by Mike Hobbs
    I'm trying to upgrade a user's machine to some better hardware. I know of Easy Transfer, but I'd rather not have to reinstall all the programs that are already present. (Some of which are no longer available, anyway). Instead, I'm trying to transfer the entire disk image from one machine to the other, but I ran into issues. If I copy the partition image over to the new machine using Clonezilla, I get errors on boot saying that I need to insert the Vista install disk and run repair. I do that, but it then says that it is unable to repair whatever it is that's broken. Next, I tried to sysprep the old machine before creating the image, but sysprep fails saying that it encountered some sort of system error. Should it be possible to sysprep any arbitrary machine, or does it only work on a relatively clean install? Could it be a missing driver that is tripping me up? The new machine is a fairly stock desktop that shouldn't need any special drivers beyond what's already present in standard Vista. Are there any foolproof methods for doing this sort of thing?

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  • Database which only holds indexes and last X records in memory?

    - by Xeoncross
    I'm looking for a data store that is very memory efficient while still allowing many object changes per second and disregarding ACID compliance for the last X records. I need this database for a server with not much memory and I can make a key-value store, document, or SQL database work. The idea is that indexes/keys are the only thing I need in memory and all the actual values/objects/rows can be saved on disk do to the low read rate (I just want index/key lookup to be fast). I also don't want records constantly being flushed to disk, so I would like the last X number of records to be held in memory so that 100 or so of them can all be written at once. I don't care if I lose the last 10 seconds worth of objects/values. I do care if the database as a whole is in danger of becoming corrupt. Is there a data-store like this?

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