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  • 'Good' programming form in maintaining / updating / accessing files by entry

    - by zhermes
    Basic Question: If I'm storying/modifying data, should I access elements of a file by index hard-coded index, i.e. targetFile.getElement(5); via a hardcoded identifier (internally translated into index), i.e. target.getElementWithID("Desired Element"), or with some intermediate DESIRED_ELEMENT = 5; ... target.getElement(DESIRED_ELEMENT), etc. Background: My program (c++) stores data in lots of different 'dataFile's. I also keep a list of all of the data-files in another file---a 'listFile'---which also stores some of each one's properties (see below, but i.e. what it's name is, how many lines of information it has etc.). There is an object which manages the data files and the list file, call it a 'fileKeeper'. The entries of a listFile look something like: filename , contents name , number of lines , some more numbers ... Its definitely possible that I may add / remove fields from this list --- but in general, they'll stay static. Right now, I have a constant string array which holds the identification of each element in each entry, something like: const string fileKeeper::idKeys[] = { "FileName" , "Contents" , "NumLines" ... }; const int fileKeeper::idKeysNum = 6; // 6 - for example I'm trying to manage this stuff in 'good' programatic form. Thus, when I want to retrieve the number of lines in a file (for example), instead of having a method which just retrieves the '3'rd element... Instead I do something like: string desiredID = "NumLines"; int desiredIndex = indexForID(desiredID); string desiredElement = elementForIndex(desiredIndex); where the function indexForID() goes through the entries of idKeys until it finds desiredID then returns the index it corresponds to. And elementForIndex(index) actually goes into the listFile to retrieve the index'th element of the comma-delimited string. Problem: This still seems pretty ugly / poor-form. Is there a way I should be doing this? If not, what are some general ways in which this is usually done? Thanks!

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  • Solr automatic startup script

    - by Camran
    I have followed this tutorial: http://wiki.apache.org/solr/SolrJetty But I cant get it working. I don't know what to put in the etc/defaults/jetty file Does anybody know how to configure this? I have Ubuntu 9 Server. Thanks

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  • Validation - Data Integrity

    - by Thomas
    A table can only store 10 records in a particular state, 10 users over 30 years for example, the others must be less than 30 years. It is a business rule and as such should be respected. How to ensure that state? Think: multiple users accessing this table.

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  • mysql query not running correctly from inside the application

    - by Mala
    I am completely stumped. Here is my php (CodeIgniter) code: function mod() { $uid = $this->session->userdata('uid'); $pid = $this->input->post('pid'); if ($this->_verify($uid,$pid)) { $name = $this->input->post('name'); $price = $this->input->post('price'); $curr = $this->input->post('curr'); $url = $this->input->post('url'); $query = $this->db->query("UPDATE items SET name=".$this->db->escape($name).", price=".$this->db->escape($price).", currency=".$this->db->escape($curr),", url=".$this->db->escape($url)." WHERE pid=".$this->db->escape($pid)." LIMIT 1"); } header('location: '.$this->session->userdata('current')); } The purpose of this code is to modify the properties (name, price, currency, url) of a row in the 'items' table (priary key is pid). However, for some reason, allowing this function to run once modifies the name, price, currency and url of ALL entries in the table, regardless of their pid and of the LIMIT 1 thing I tacked on the end of the query. It's as if the last line of the query is being completely ignored. As if this wasn't strance enough, I replaced "$query = $this->db->query(" with an "echo" to see the SQL query being run, and it outputs a query much like I would expect: UPDATE items SET name='newname', price='newprice', currency='newcurrency', url='newurl' WHERE pid='10' LIMIT 1 Copy-pasting this into a MySQL window acts exactly as I want: it modifies the row with the selected pid. What is going on here???

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  • MySQL "NULL" questions

    - by Camran
    I have a table with several columns. Sometimes some of these column fields may be empty (ie. I won't use them in some cases). My questions: Would it be smart to set them to NULL in phpmyadmin? What does the "NULL" property actually do? Would I gain anything at all by setting them to NULL? Is it possible to use a NULL field the same way even though it is set to null?

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  • Beginner having difficulty with SQL query

    - by Vulcanizer
    Hi, I've been studying SQL for 2 weeks now and I'm preparing for an SQL test. Anyway I'm trying to do this question: For the table: 1 create table data { 2 id int, 3 n1 int not null, 4 n2 int not null, 5 n3 int not null, 6 n4 int not null, 7 primary key (id) 8 } I need to return the relation with tuples (n1, n2, n3) where all the corresponding values for n4 are 0. The problem asks me to solve it WITHOUT using subqueries(nested selects/views) It also gives me an example table and the expected output from my query: 01 insert into data (id, n1, n2, n3, n4) 02 values (1, 2,4,7,0), 03 (2, 2,4,7,0), 04 (3, 3,6,9,8), 05 (4, 1,1,2,1), 06 (5, 1,1,2,0), 07 (6, 1,1,2,0), 08 (7, 5,3,8,0), 09 (8, 5,3,8,0), 10 (9, 5,3,8,0); expects (2,4,7) (5,3,8) and not (1,1,2) since that has a 1 in n4 in one of the cases. The best I could come up with was: 1 SELECT DISTINCT n1, n2, n3 2 FROM data a, data b 3 WHERE a.ID <> b.ID 4 AND a.n1 = b.n1 5 AND a.n2 = b.n2 6 AND a.n3 = b.n3 7 AND a.n4 = b.n4 8 AND a.n4 = 0 but I found out that also prints (1,1,2) since in the example (1,1,2,0) happens twice from IDs 5 and 6. Any suggestions would be really appreciated.

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  • What tool for managing Oracle DB do you suggest?

    - by Artic
    What tool for managing Oracle DB do you suggest? I need to execute scripts and manage data in tables and develop some scripts and packages. I'v tried SQL developer and actually don't like it. Want some more features for developing (debug, code assist, integrated help and so on.)

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  • SELECT only a certain set of rows at a time

    - by prmatta
    I need to select data from one table and insert it into another table. Currently the SQL looks something like this: INSERT INTO A (x, y, z) SELECT x, y, z FROM B b WHERE ... However, the SELECT is huge, resulting in over 2 millions rows and we think it is taking up too much memory. Informix, the db in this case, runs out of virtual memory when the query is run. How would I go about selecting and inserting a set of rows (say 2000)? Given that I don't think there are any row ids etc.

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  • What's the best way to test MSSQL connection programmatically?

    - by backslash17
    I need to develop a single routine that will be fired each 5 minutes to check if a list of MSSQL servers (10 to 12) are up and running. I can try to obtain a simple query in each one of the servers but this means that I have to create a table, view or stored procedure in every server, even if I use any already made SP I need to have a registered user in each server too. The servers are not in the same phisical location so having those requirements would be a complex task. Is there a way to simply "ping" from c# one MSSQL server? Thanks in advance!

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  • getting smallest of coordinates that differ by N or more in Python

    - by user248237
    suppose I have a list of coordinates: data = [[(10, 20), (100, 120), (0, 5), (50, 60)], [(13, 20), (300, 400), (100, 120), (51, 62)]] and I want to take all tuples that either appear in each list in data, or any tuple that differs from all tuples in lists other than its own by 3 or less. How can I do this efficiently in Python? For the above example, the results should be: [[(100, 120), # since it occurs in both lists (10, 20), (13, 20), # since they differ by only 3 (50, 60), (51, 60)]] (0, 5) and (300, 400) would not be included, since they don't appear in both lists and are not different from elements in lists other than their own by 3 or less. how can this be computed? thanks.

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  • PHP: Which DB/DB Engine supports search well?

    - by KeyStroke
    Hi, I'm starting a site which relies heavily on search. While it's probably going to search basic meta data in the beginning, it might grow to something bigger in the future. So which DB/DB Engine is best in your opinion when it comes to search performance and future scalability? Appreciate your help

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  • When/Why to use Cascading in SQL Server?

    - by Joel Coehoorn
    When setting up foreign keys in SQL Server, under what circumstances should you have it cascade on delete or update, and what is the reasoning behind it? This probably applies to other databases as well. I'm looking most of all for concrete examples of each scenario, preferably from someone who has used them successfully.

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  • How do you debug MySQL stored procedures?

    - by Cory House
    My current process for debugging stored procedures is very simple. I create a table called "debug" where I insert variable values from the stored procedure as it runs. This allows me to see the value of any variable at a given point in the script, but is this is there a better way to debug MySQL stored procedures?

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  • Three-way full outer join in SQLite

    - by Vince
    I have three tables with a common key field, and I need to join them on this key. Given SQLite doesn't have full outer or right joins, I've used the full outer join without right join technique on Wikipedia with much success. But I'm curious, how would one use this technique to join three tables by a common key? What are the efficiency impacts of this (the current query takes about ten minutes)? Thanks!

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  • Which MySql line is faster:

    - by Camran
    I have a classified_id variable which matches one document in a MySql table. I am currently fetching the information about that one record like this: SELECT * FROM table WHERE table.classified_id = $classified_id I wonder if there is a faster approach, for example like this: SELECT 1 FROM table WHERE table.classified_id = $classified_id Wont the last one only select 1 record, which is exactly what I need, so that it doesn't have to scan the entire table but instead stops searching for records after 1 is found? Or am I dreaming this? Thanks

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  • Many tables for many users?

    - by Seagull
    I am new to web programming, so excuse the ignorance... ;-) I have a web application that in many ways can be considered to be a multi-tenant environment. By this I mean that each user of the application gets their own 'custom' environment, with absolutely no interaction between those users. So far I have built the web application as a 'single user' environment. In other words, I haven't actually done anything to support multi-users, but only worked on the functionality I want from the app. Here is my problem... What's the best way to build a multi-user environment: All users point to the same 'core' backend. In other words, I build the logic to separate users via appropriate SQL queries (eg. select * from table where user='123' and attribute='456'). Each user points to a unique tablespace, which is built separately as they join the system. In this case I would simply generate ALL the relevant SQL tables per user, with some sort of suffix for the user. (eg. now a query would look like 'select * from table_ where attribute ='456'). In short, it's a difference between "select * from table where USER=" and "select * from table_USER".

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