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• Why would you want a case sensitive database?

  - by Khorkrak

  What are some reasons for choosing a case sensitive collation over a case insensitive one? I can see perhaps a modest performance gain for the DB engine in doing string comparisons. Is that it? If your data is set to all lower or uppercase then case sensitive could be reasonable but it's a disaster if you store mixed case data and then try to query it. You have then apply a lower() function on the column so that it'll match the corresponding lower case string literal. This prevents index usage in every dbms. So wondering why anyone would use such an option.

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• What are some best practises and "rules of thumb" for creating database indexes?

  - by Ash

  I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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• Thinking of an Inner Join as a Cross Join and then satisfying some condition(s)?

  - by Jian Lin

  It seems like the safest way to think of an Inner Join is to think of it as a Cross Join and then satisfying some condition(s)? Because the equi-join can be obvious, but the non-equi-join can be a bit confusing. But if we always use the Cross Join, and then filter out the ones satisfying the condition, then we get the resulting table. In other words, we can always analyze it by using the first record on the left table, and then go through every single records on the right, and then repeat that for 2nd record on the left, and for the 3rd, 4th, ... etc. So in our mind, we can analyze it using this way, and it is like O(n^2), although what happens in the DBMS maybe that it is a lot faster (when an index is present). Is there another good way to think of it besides this method?

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• Linq to SQL EntitySet Records causing duplicate insertion

  - by Savvas Sopiadis

  In a WPF application i'm using Linq to SQL in a multi tier application. (This is an archailogy photo filing application), so every excavation has its corresponding Pictures, thus a one-to-many relationship. This relationship is correctly created by SQLMetal (which i'm using to create the POCOs). So here is the situation i 'm having trouble with: Saving changes (either of new or altered objects) is done through UnitOfWork() pattern this way: using (IUnitOfWork unitOfWork = UnitOfWork.Begin()) { //if this is a new record if (SelectedExcavation.excavation.ExcavationId == 0) { IsNewRecord = true; excavService.Add(SelectedExcavation.excavation); } //send the actual changes to the dbms unitOfWork.Commit(); } Everything works fine! BUTTTT!!! Whenever a record gets updated which has (already at least one ) corresponding Picture Record: 1) a new Excavation Record is inserted 2) the current Excavation Record gets updated 3) the previous Picture Record gets its Id changed to the newly created ExcavationId What is going on under the hood? Does Linq to SQL not handle such simple update scenarios? Thanks in advance

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• Is it possible to have a tableless select with multiple rows?

  - by outis

  A SELECT without a FROM clause gets us a multiple columns without querying a table: SELECT 17+23, REPLACE('bannanna', 'nn', 'n'), RAND(), CURRENT_TIMESTAMP; How can we write a query that results in multiple rows without referring to a table? Basically, abuse SELECT to turn it into a data definition statement. The result could have a single column or multiple columns. I'm most interested in a DBMS neutral answer, but others (e.g. based on UNPIVOT) are welcome. There's no technique application behind this question; it's more theoretical than practical.

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• It seems like the safest way to think of an Inner Join is to think of it as a Cross Join and then sa

  - by Jian Lin

  It seems like the safest way to think of an Inner Join is to think of it as a Cross Join and then satisfying some condition(s)? Because the equi-join can be obvious, but the non-equi-join can be a bit confusing. But if we always use the Cross Join, and then filter out the ones satisfying the condition, then we get the resulting table. In other words, we can always analyze it by using the first record on the left table, and then go through every single records on the right, and then repeat that for 2nd record on the left, and for the 3rd, 4th, ... etc. So in our mind, we can analyze it using this way, and it is like O(n^2), although what happens in the DBMS maybe that it is a lot faster (when an index is present). Is there another good way to think of it besides this method?

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• Nested joins hide table names

  - by Sergio

  Hi: I have three tables: Suppliers, Parts and Types. I need to join all of them while discriminating columns with the same name (say, "id") in the three tables. I would like to successfully run this query: CREATE VIEW Everything AS SELECT Suppliers.name as supplier, Parts.id, Parts.description, Types.typedesc as type FROM Suppliers JOIN (Parts JOIN Types ON Parts.type_id = Types.id) ON Suppliers.id = Parts.supplier_id; My DBMS (sqlite) complains that "there is not such a column (Parts.id)". I guess it forgets table names once the JOIN is done but then how can I refer to the column id that belongs to the table Parts?

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• How to force adodb php library to use lowercase field names

  - by spam

  I'm trying to use adodb for db access in my webapp. However my hosting provider has mysql case sensitive, and I have all my fields in lowercase. But when I call getInsertSQL function, I got them in uppercase. Is there a way to force adodb to use lowercase? I tried with define('ADODB_ASSOC_CASE', 0); $ADODB_ASSOC_CASE = 0; But it seems to be ignored as the constant is suppose to be used only with oracle, MSSQL and other DBMS $conn = &ADONewConnection($this->DbType); $conn = PConnect($dbServer,$dbUser, $dbPassword,$database); $tableName = "sample"; $insertSQL = $conn->GetInsertSQL($tableName,$objDB); And I got the SQL statement with the column names in uppercase.

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• Simple ASP function question

  - by J Harley

  Good Morning, I have got the following function: FUNCTION queryDatabaseCount(sqlStr) SET queryDatabaseCountRecordSet = databaseConnection.Execute(sqlStr) If queryDatabaseCountRecordSet.EOF Then queryDatabaseCountRecordSet.Close queryDatabaseCount = 0 Else QueryArray = queryDatabaseCountRecordSet.GetRows queryDatabaseCountRecordSet.Close queryDatabaseCount = UBound(QueryArray,2) + 1 End If END FUNCTION And the following dbConnect: SET databaseConnection = Server.CreateObject("ADODB.Connection") databaseConnection.Open "Provider=SQLOLEDB; Data Source ="&dataSource&"; Initial Catalog ="&initialCatalog&"; User Id ="&userID&"; Password="&password&"" But for some reason I get the following error: ADODB.Recordset error '800a0e78' Operation is not allowed when the object is closed. /UBS/DBMS/includes/blocks/block_databaseoverview.asp, line 30 Does anyone have any suggestions? Many Thanks, Joel

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• Need a Count, but Multiple other fields

  - by user3727752

  I have a table that looks like this: person trip_id date home destination joe 1 3/10 chicago new york joe 2 4/10 chicago l.a. joe 3 5/10 chicago boston luther 4 3/12 new york chicago luther 5 3/18 new york boston I want to get a result like person trips firstDate home joe 3 3/10 chicago luther 2 3/12 new york Currently I've got Select person, count(trip_id) as trips, min(date) as firstDate from [table] group by person order by firstDate I can't figure out how to get home in there as well. Home is always unique to the person. But my DBMS doesn't know that. Is there an easy way around this problem? Appreciate it.

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• Document/Scripts management for R code

  - by harshsinghal

  Hi useRs, I am looking for a solution that allows me to keep a track of a multitude of R scripts that I create for various projects and purposes. Some scripts are easily tracked to specific projects, whereas others are "convenience" functions created to serve a set of tasks. Is there a way I can create a central DB and query it to find which scripts match most appropriately? I could create a system using a DBMS manually, but are users aware of anything in general or specific to R, that comes in the form of a software tool (maybe FOSS) ?

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• How to update SQL Server database from multiple data sources for ASP.Net MVC 4 application

  - by shaz

  I have 10+ SQL Server databases, from where I would use one table from each database to display information using the application that I am creating. For instance, DB1, DB2....DB10. NewDB (Account, Country, Costcenter....etc.). I have started with creating a new database which would contain all the information from all those 10+ databases. However, I am confused in many cases. First of all what process should I follow? Shall I create a table (in new database) with the same structure as the actual data source and insert data from actual data source to new database? Should I be doing this on the DBMS? If so, is it some scripting? (hint expected since very new to this) I am creating a report generation application which has 10+ data sources. I need some hint which way should I proceed? Thanks for advice/help in advance.

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• Referencing surrogate key

  - by Arman

  I have a table that has an autoincrement surrogate key. I want to use it as a foreign key of my other table. The thing is, I cant figure out how I can reference it to that table, because it is nearly impossible to determine what I have to reference(the actual value of the surrogate key). Please be noted that what I am trying to do is adding a tuple/record through my program(outside the dbms). The process is: Add a new record in Table1 and generate an autoincrement key. Update Add a new record in Table2 and reference its foreign key to the primary key of Table1. Update My question is : HOW do I store the foreign key if I didnt know what is it?

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• Is MS Access still the most efficient RAD tool for small-scale custom apps?

  - by FastAl

  Of the many other development tools I've used, nothing holds a candle to the 'Functionality to Development Effort' ratio of MS Access. The reason I am asking is that I have been out of the language selection process for a few years, working on a large .Net system, and am only anecdotally familiar with the latest development tools outside the .Net world. I'm well aware of the limitations of Access, but for a limited concurrency (usually only 1 user at a time), small business, custom app, has anybody found a comparable end-to-end solution or combination that comes close? It doesn't have to be free, open source, or even Windows based. It just has to allow the same speed of development and maintenance, and maybe even provide some additional amenities like seamless autointegration with a server-based DB Engine (like Access does with its own 'Jet' dbms), better web support, and a file format more compatible with source control. I don't want to miss out on anything. Please share your development experience with your suggestions. Thanks.

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• what good orm api will work well with scala or erlang

  - by Emotu Balogun

  I'm considering taking up scala programming but i'm really concerned about what will become of my ORM based applications. I currently use hibernate as my ORM and i find it a really reliable tool. I'd like to know if there's any ORM tool as efficient but written in scala, or will hibernate work seamlessly with it. i don't want to have to start writing endless sql queries again (like the days of JDBC). I also have the same thought about erlang. is there a good orm out there for erlang?? and can i use erlang with other DBMS like oracle and mysql with ORM

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• Alter multiple tables' columns length

  - by gdoron

  So, we just found out that 254 tables in our Oracle DBMS have one column named "Foo" with the wrong length- Number(10) instead of Number(3). That foo column is a part from the PK of the tables. Those tables have other tables with forigen keys to it. What I did is: backed-up the table with a temp table. Disabled the forigen keys to the table. Disabled the PK with the foo column. Nulled the foo column for all the rows. Restored all the above But now we found out it's not just couple of tables but 254 tables. Is there an easy way, (or at least easier than this) to alter the columns length? P.S. I have DBA permissions.

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• SQL server connection trouble in network but not in local

  - by user1517139

  for the first time that I would work with SQL SERVER 2005, the jdbc connection doesn't work in the network I searched and have done thousand of things that doesn't work, i also want to precise that i already had worked with other DBMS, so here is the problem: when i try to connect by jdbc from the machine where sql server is installed everything work just fine, but when i try from a different machine, the jdbc is unable to create the connection, i already checked that TCP/IP communication is enabled that the port (not dynamically assigned) is 1433 and i even tried with different ports, i also tried with the same driver and different driver, i checked that i was able to communicate with the http server (who is installed in the machine where SQL server is installed) and it works but that jdbc connection can't, i tried thousand of things until i forgot some of them, someone please help

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• Are conditional subqueries optimized out, if the condition is false?

  - by Tobias Schulte

  I have a table foo and a table bar, where each foo might have a bar (and a bar might belong to multiple foos). Now I need to select all foos with a bar. My sql looks like this SELECT * FROM foo f WHERE [...] AND ($param IS NULL OR (SELECT ((COUNT(*))>0) FROM bar b WHERE f.bar = b.id)) with $param being replaced at runtime. The question is: Will the subquery be executed even if param is null, or will the dbms optimize the subquery out? We are using mysql, mssql and oracle. Is there a difference between these regarding the above?

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• How to join by column name

  - by Daniel Vaca

  I have a table T1 such that gsdv |nsdv |esdv ------------------- 228.90 |216.41|0.00 and a table T2 such that ds |nm -------------------------- 'Non-Revenue Sales'|'ESDV' 'Gross Sales' |'GSDV' 'Net Sales' |'NSDV' How do I get the following table? ds |nm |val --------------------------------- 'Non-Revenue Sales'|'ESDV'|0.00 'Gross Sales' |'GSDV'|228.90 'Net Sales' |'NSDV'|216.41 I know that I can this by doing the following SELECT ds,nm,esdv val FROM T1,T2 WHERE nm = 'esdv' UNION SELECT ds,nm,gsdv val FROM T1,T2 WHERE nm = 'gsdv' UNION SELECT ds,nm,nsdv val FROM T1,T2 WHERE nm = 'nsdv' but I am looking for a more generic/nicer solution. I am using Sybase, but if you can think of a way to do this with other DBMS, please let me know. Thanks.

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• Oracle checking existence before deletion in a trigger

  I have analyzed a hibernate generated oracle database and discovered that a delete of a row from a single table will spawn the firing of 1200+ triggers in order to delete the related rows in child tables. The triggers are all auto-generated the same - an automatic delete of a child row without checking for existence first. As it is impossible to predict which child tables will actually have related rows, I think a viable solution to preventing the firing of the cascaded delete down a deeply branched completely empty limb, would be to check for the existence of a related row before attempting to delete. In other dbms', I could simply state " if exists....." before deleting. Is there a comparable way to do this in oracle?

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• MySQL column names and aliases

  - by user329820

  hi, I have read that after select we use column-names but I have found a statement that was like this: SELECT 'A' FROM T WHERE A = NULL; would you lease help me? thanks (A is a column- name here?) my DBMS is MySQL EDITED : the exact question is this that: Will the above statement produce a row (select all that apply)? Notice that ANSI_NULLS is OFF. I want to know that the above statement will work? because some of you said that we should write IS NULL instead of =null

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• DXVA and ATI.... what am I missing?

  - by Shiki

  ATI Radeon HD3650 ffdshow (the one comes with CCCP 2010-10 AND the latest from Free-codecs site) Catalyst 10.12 Latest DirectX, Windows 7 HP x64 If I try to play it simply, the player (mpc-hc) won't use the acceleration. If I disable checks, I get artifacts. Back then it worked perfectly with my Intel and ATI too (Lenovo ThinkPad T500, switchable graphics). This only appeared recently. What should I do? What am I missing? If possible, I don't really want to downgrade drivers (waaa ATI drivers s.ck ... sorry but.. honestly), because the older one got a buggy DP driver so my external display gets a totally wrong resolution. Info about the media file: Video: Format : AVC Format/Info : Advanced Video Codec Format profile : [email protected] Codec ID : V_MPEG4/ISO/AVC Writing library : x264 core 88 r1462 7fcffde Encoding settings : cabac=1 / ref=8 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=8 / psy=1 / psy_rd=0.80:0.20 / mixed_ref=1 / me_range=24 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-3 / threads=3 / sliced_threads=0 / nr=0 / decimate=1 / mbaff=0 / constrained_intra=0 / bframes=8 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / wpredb=1 / wpredp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=16.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00 The sample file I'm testing at the moment: [Coalgirls]_Kiddy_Girl-and_01_(1920x1080_Blu-Ray_FLAC)_[91428679].mkv (I tried many x264 files, no use.) Artifacts

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• How to make Virtualbox, OpenVPN, and Win2008 Web R2 like one another?

  - by Aquitaine

  Back with web developer guy wearing net admin hat. Hopefully this is an easy one. We have two servers on a public network at a hosted facility. Server A is our public-facing web server and server B is our database server. Both are running Windows 2008 Server R2 Web Edition. We want Server B isolated from everything except Server A, such that anyone who has to connect to server B goes through the VPN on Server A. It's not perfect since we have no access to do this on the router side, but it's what we've got. We've set up VirtualBox and OpenVPN Access Server on Server A. It has one network interface set to 'NAT' mode, such that OpenVPN gets its IP at 10.0.2.x, and to connect to the OpenVPN interface, I go to the local IP for the Virtualbox network adapter, 192.168.56.x, which works as I configured the appropriate ports using VBoxManage. My question is, do I need to be using Bridged Networking and give the VPN server its own IP, or is there some way to tell the server (either Windows or the Virtualbox OpenVPN) that 'any public connection on the real external IP on port X should be directed to this internal LAN address of 192.168.1.x on port Y'? OpenVPN itself doesn't seem to be aware of the server's real external IP unless we put it in Bridged networking mode; is that necessary or advisable? We're without RRAS since this is Web edition, but I feel like what we're going for is pretty simple. Thanks! Aq

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• SQL Server Installation: Is it 32 or 64 bit?

  - by CapBBeard

  Recently I was performing an OS upgrade on one of our DB servers, moving from Server 2003 to Server 2008. The DBMS is SQL Server 2005. While reinstalling SQL on the new Windows installation, I went to another of our DB servers to verify a couple of settings. Now, I always thought this second server was Server 2003 x64 + SQL 2005 x64 (from what I'd been told), but I now have my doubts about this. I now suspect that it is in fact only 32 bit SQL, however I'd like to verify this. Here's some details: The OS is definitely 64 bit. xp_msver shows Platform as NT INTEL X86 SELECT @@VERSION shows Microsoft SQL Server 2005 - 9.00.4035.00 (Intel X86)... However sqlservr.exe is not shown with '* 32' in taskmgr, does anyone know why this is the case, if it is in fact 32 bit as claimed? Despite this, it does seem to be running out of the x86 program files folder. If I do the same checks on a confirmed 64 bit installation, it does give back the expected 64 bit readings, which can only prove that this server in question is only running in 32 bit. Now, that being the case, the question arises about how much memory this '32 bit' install can use. Task manager reports about 3.5GB memory usage for sqlservr.exe (The server has 16GB physical). I suspect that AWE has not been configured at all, and therefore the server will be significantly under-utilised (remembering that the OS is 64 bit) if SQL is simply using a 32bit address space. Is this assumption correct? I feel the server should have SQL reinstalled as 64 bit in order to fully utilise the hardware platform, however it is currently heavily in production; this will be no easy task. I suspect we may just have to configure AWE correctly and let it be for the time being (Unless this is a bad idea?). I apologise that this question is a little vague/lost; I'm no SQL expert, just trying to get a handle on what's going on here.

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• SQL Server Installation: Is it 32 or 64 bit?

  - by CapBBeard

  Hi, Recently I was performing an OS upgrade on one of our DB servers, moving from Server 2003 to Server 2008. The DBMS is SQL Server 2005. While reinstalling SQL on the new Windows installation, I went to another of our DB servers to verify a couple of settings. Now, I always thought this second server was Server 2003 x64 + SQL 2005 x64 (from what I'd been told), but I now have my doubts about this. I now suspect that it is in fact only 32 bit SQL, however I'd like to verify this. Here's some details: The OS is definitely 64 bit. xp_msver shows Platform as NT INTEL X86 SELECT @@VERSION shows Microsoft SQL Server 2005 - 9.00.4035.00 (Intel X86)... However sqlservr.exe is not shown with '* 32' in taskmgr, does anyone know why this is the case, if it is in fact 32 bit as claimed? Despite this, it does seem to be running out of the x86 program files folder. If I do the same checks on a confirmed 64 bit installation, it does give back the expected 64 bit readings, which can only prove that this server in question is only running in 32 bit. Now, that being the case, the question arises about how much memory this '32 bit' install can use. Task manager reports about 3.5GB memory usage for sqlservr.exe (The server has 16GB physical). I suspect that AWE has not been configured at all, and therefore the server will be significantly under-utilised (remembering that the OS is 64 bit) if SQL is simply using a 32bit address space. Is this assumption correct? I feel the server should have SQL reinstalled as 64 bit in order to fully utilise the hardware platform, however it is currently heavily in production; this will be no easy task. I suspect we may just have to configure AWE correctly and let it be for the time being (Unless this is a bad idea?). I apologise that this question is a little vague/lost; I'm no SQL expert, just trying to get a handle on what's going on here.

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