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  • Why is rails setting ":null => false" on all my columns in schema.rb?

    - by ryeguy
    Even if I never specify :null => false in my migrations that initially add columns to tables, rails still generates code in schema.rb that specifies the columns as having :null => false. Why is this? If I develop on my box, and then use rake db:schema:load on my production box, I'm going to get very different behavior! Edit: Even if I delete schema.rb and run rake db:schema:dump, it still puts :null => false on the new schema even if it isn't defined like that in the actual database. It seems it can't tell whether or not a column is marked as allowing nulls. I'm using SQLite if that helps.

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  • JPQL: What kind of objects contains a result list when querying multiple columns?

    - by Bunkerbewohner
    Hello! I'm trying to do something which is easy as pie in PHP & Co: SELECT COUNT(x) as numItems, AVG(y) as average, ... FROM Z In PHP I would get a simple array like [{ numItems: 0, average: 0 }] which I could use like this: echo "Number of Items: " . $result[0]['numItems']; Usually in JPQL you only query single objects or single columns and get Lists types, for example List or List. But what do you get, when querying multiple columns?

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  • Why is selecting specified columns, and all, wrong in Oracle SQL?

    - by TomatoSandwich
    Say I have a select statement that goes.. select * from animals That gives a a query result of all the columns in the table. Now, if the 42nd column of the table animals is is_parent, and I want to return that in my results, just after gender, so I can see it more easily. But I also want all the other columns. select is_parent, * from animals This returns ORA-00936: missing expression. The same statement will work fine in Sybase, and I know that you need to add a table alias to the animals table to get it to work ( select is_parent, a.* from animals ani), but why must Oracle need a table alias to be able to work out the select?

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  • Generating a .CSV with Several Columns - Use a Dictionary?

    - by Qanthelas
    I am writing a script that looks through my inventory, compares it with a master list of all possible inventory items, and tells me what items I am missing. My goal is a .csv file where the first column contains a unique key integer and then the remaining several columns would have data related to that key. For example, a three row snippet of my end-goal .csv file might look like this: 100001,apple,fruit,medium,12,red 100002,carrot,vegetable,medium,10,orange 100005,radish,vegetable,small,10,red The data for this is being drawn from a couple sources. 1st, a query to an API server gives me a list of keys for items that are in inventory. 2nd, I read in a .csv file into a dict that matches keys with item name for all possible keys. A snippet of the first 5 rows of this .csv file might look like this: 100001,apple 100002,carrot 100003,pear 100004,banana 100005,radish Note how any key in my list of inventory will be found in this two column .csv file that gives all keys and their corresponding item name and this list minus my inventory on hand yields what I'm looking for (which is the inventory I need to get). So far I can get a .csv file that contains just the keys and item names for the items that I don't have in inventory. Give a list of inventory on hand like this: 100003,100004 A snippet of my resulting .csv file looks like this: 100001,apple 100002,carrot 100005,radish This means that I have pear and banana in inventory (so they are not in this .csv file.) To get this I have a function to get an item name when given an item id that looks like this: def getNames(id_to_name, ids): return [id_to_name[id] for id in ids] Then a function which gives a list of keys as integers from my inventory server API call that returns a list and I've run this function like this: invlist = ServerApiCallFunction(AppropriateInfo) A third function takes this invlist as its input and returns a dict of keys (the item id) and names for the items I don't have. It also writes the information of this dict to a .csv file. I am using the set1 - set2 method to do this. It looks like this: def InventoryNumbers(inventory): with open(csvfile,'w') as c: c.write('InvName' + ',InvID' + '\n') missinginvnames = [] with open("KeyAndItemNameTwoColumns.csv","rb") as fp: reader = csv.reader(fp, skipinitialspace=True) fp.readline() # skip header invidsandnames = {int(id): str.upper(name) for id, name in reader} invids = set(invidsandnames.keys()) invnames = set(invidsandnames.values()) invonhandset = set(inventory) missinginvidsset = invids - invonhandset missinginvids = list(missinginvidsset) missinginvnames = getNames(invidsandnames, missinginvids) missinginvnameswithids = dict(zip(missinginvnames, missinginvids)) print missinginvnameswithids with open(csvfile,'a') as c: for invname, invid in missinginvnameswithids.iteritems(): c.write(invname + ',' + str(invid) + '\n') return missinginvnameswithids Which I then call like this: InventoryNumbers(invlist) With that explanation, now on to my question here. I want to expand the data in this output .csv file by adding in additional columns. The data for this would be drawn from another .csv file, a snippet of which would look like this: 100001,fruit,medium,12,red 100002,vegetable,medium,10,orange 100003,fruit,medium,14,green 100004,fruit,medium,12,yellow 100005,vegetable,small,10,red Note how this does not contain the item name (so I have to pull that from a different .csv file that just has the two columns of key and item name) but it does use the same keys. I am looking for a way to bring in this extra information so that my final .csv file will not just tell me the keys (which are item ids) and item names for the items I don't have in stock but it will also have columns for type, size, number, and color. One option I've looked at is the defaultdict piece from collections, but I'm not sure if this is the best way to go about what I want to do. If I did use this method I'm not sure exactly how I'd call it to achieve my desired result. If some other method would be easier I'm certainly willing to try that, too. How can I take my dict of keys and corresponding item names for items that I don't have in inventory and add to it this extra information in such a way that I could output it all to a .csv file? EDIT: As I typed this up it occurred to me that I might make things easier on myself by creating a new single .csv file that would have date in the form key,item name,type,size,number,color (basically just copying in the column for item name into the .csv that already has the other information for each key.) This way I would only need to draw from one .csv file rather than from two. Even if I did this, though, how would I go about making my desired .csv file based on only those keys for items not in inventory?

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  • How to do insert one row from one table to another table(what has less columns)?

    - by chobo2
    Hi I am trying to find rows that are not in one table and insert them into another. The table I am trying to insert into has less columns then the other one. These columns are null but it would be cool if I could hardcode a value before I do the insert. But I am having so much trouble with just trying to get it to insert. I have something like this SELECT p.ProductId, p.ProductName INTO SomeTable FROM Product as p WHERE p.ProductName != 'iPad' I will get a error like this though Msg 4104, Level 16, State 1, Line 1 The multi-part identifier "p.ProductId" could not be bound. I am not sure what I am doing wrong. I copied and pasted the names in so I don't think it is a spelling mistake. I am using ms sql 2005 express.

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  • How to set DataGridView columns text format to uppercase by adding new property?

    - by Jooj
    Hello, I have a custom DataGridView control and want to set the text format for custom columns in the designer (CellStyle builder). Let's say I want to make the text format to uppercase. After searching about this I've found some solutions with adding new events and then changing the text format but this is not what I want. I want to add a new property to all designed columns and there set or change the text format. How to do this? Thank and best regards.

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  • Does the order of the columns in a SELECT statement make a difference?

    - by Frank Computer
    This question was inspired by a previous question posted on SO, "Does the order of the WHERE clause make a differnece?". Would it improve a SELECT statement's performance if the the columns used in the WHERE section are placed at the begining of the SELECT statement? example: SELECT customer.id, transaction.id, transaction.efective_date, transaction.a, [...] FROM customer, transaction WHERE customer.id = transaction.id; I do know that limiting the list of columns to only the needed ones in a SELECT statement improves performance as opposed to using SELECT * because the current list is smaller.

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  • Is an index required for columns in ON clause?

    - by newbie
    Do I have to create an index on columns referenced in Joins? E.g. SELECT * FROM left_table INNER JOIN right_table ON left_table.foo = right_table.bar WHERE ... Should I create indexes on left_table(foo), right_table(bar), or both? I noticed different results when I used EXPLAIN (Postgresql) with and without indexes and switching around the order of the comparison (right_table.bar = left_table.foo) I know for sure that indexes are used for the left of the WHERE clause but I am wondering whether I need indexes for columns listed in ON clauses.

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  • Multiple classes in a single .cs file - good or bad?

    - by Sergio
    Is it advisable to create multiple classes within a .cs file or should each .cs file have an individual class? For example: public class Items { public class Animal { } public class Person { } public class Object { } } Dodging the fact for a minute that this is a poor example of good architecture, is having more than a single class in a .cs file a code smell?

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  • How can I use multiple meshes per entity without breaking one component of a single type per entity?

    - by Mathias Hölzl
    We are just switching from a hierarchy based game engine to a component based game engine. My problem is that when I load a model which has has a hierarchy of meshes and the way I understand is that a entity in a component based system can not have multiple components of the same type, but I need a "meshComponent" for each mesh in a model. So how could I solve this problem. On this side they implemented a Component based game engine: http://cowboyprogramming.com/2007/01/05/evolve-your-heirachy/

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  • Multiple Depends/Recommends/[…] in a control file?

    - by miK
    Is it possible to have multiple lines for any type of field in a dpkg control file? This is not about line continuation, but e.g. Depends interspersed with Recommends like so: Depends: git, etckeeper, apt-file Recommends: equivs Depends: mplayer, pidgin, dlocate, pwsafe, ciso Recommends: aria2 And so on. Is this allowed, is it unspecified (and some tool is going to cough on it) or is it explicitly forbidden? (Couldn't find anything in debian-policy, either)

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  • Can a NodeJS webserver handle multiple hostnames on the same IP?

    - by Matthew Patrick Cashatt
    I have just begun learning NodeJS and LOVE it so far. I have set up a Linux box to run it and, in learning to use the event-driven model, I am curious if I can use a common IP for multiple domain names. Could I point, for example, www.websiteA.com, www.websiteB.com, and www.websiteC.com all to the same IP (node webserver) and then route to the appropriate source files based on the request? Would this cause certain doom when it came to scaling to any reasonable size?

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  • Should I use multiple column primary keys or add a new colum?

    - by Covar
    My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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  • Multiple classes in a single .cs file - good or bad?

    - by Sergio
    Is it advisable to create multiple classes within a .cs file or should each .cs file have an individual class? For example: public class Items { public class Animal { } public class Person { } public class Object { } } Dodging the fact for a minute that this is a poor example of good architecture, is having more than a single class in a .cs file a code smell?

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  • Is it possible to use multiple desktop environments on same system?

    - by Kshitiz Sharma
    I am using Ubuntu 12.04. I want to try out KDE and other desktop environments. But I'm not sure if I'll like them enough to switch permanently. I want to be safe and make a transition in a piecemeal fashion. Is it possible to install KDE on Ubuntu and yet not do away with the default Unity shell? Could I install multiple desktop environments and switch between them by tweaking some startup configuration and then rebooting?

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  • Using stored procedure to call multiple packages at the same time from SSIS Catalog (SSISDB.catalog.start_execution) resulted in deadlock

    - by Kevin Shyr
    Refer to my previous post (http://geekswithblogs.net/LifeLongTechie/archive/2012/11/14/time-to-stop-using-ldquoexecute-package-taskrdquondash-a-way-to.aspx) about dynamic package calling and multiple packages execution in these posts: I only saw this twice, other times the stored procedure was able to call the packages successfully.  After the service pack, I haven't seen it...yet. http://support.microsoft.com/kb/2699720

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  • Should I use multiple column primary keys or add a new column?

    - by Covar
    My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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  • How can I sync between multiple threads so that their transaction ID be unique without using mutex?

    - by poly
    I'm writing an application in C that requires multiple threads to request a unique transaction ID from a function as shown below; struct list{ int id; struct list *next }; function generate_id() { linked-list is built here to hold 10 millions } How can I sync between two or more threads so that their transaction ID be unique among them without using mutex, is it possible? Please share anything even if I need to change linked list to something else.

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  • How to type multiple characters on a mac with a single click?

    - by Yuval
    On a Windows machine, clicking and holding a keyboard key results in the key being types multiple times. For example, if I click and hold 'q' for a few seconds, I end up with the following: qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq Similarly, I can click and hold the Backspace key to delete multiple characters. On a Mac, it seems, clicking and holding a key for several seconds results in the key being types only once. To type it repeatedly, it is necessary to psychically click it multiple times. I'm unclear about whether that is a bug or a supposed-feature, but I am interested in replicating this functionality on a Mac. Any ideas? Thanks!

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  • Windows 7 side Taskbar: how to have multiple icon columns?

    - by user151426
    NOTE: I know this can be done with the taskbar on the bottom. I seek the solution for a taskbar on the side. I attached a picture of what I mean. In the screenshots, you can see that my taskbar program icons are arranged in a single column. I want to be able to have multiple columns. This would mean arranging the icons into squares and have them be placed side by side, as well as above and below one another. This can be accomplished with taskbar being on the bottom of the screen, however, I require this arrangement when I have my taskbar on the side of my screen. Currently if I expand the taskbar horizontally, it only stretches out the icons horizontally rather than turn them into small squares to make room for side by side and placement of icons. Additional icons that I add to my current taskbar are only accessible by using the horizontal scroll bar that appears at the bottom of the taskbar when there is no more space to accommodate any more icons.

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