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• What to read as a good intro and quickstart to aspect-oriented programming and metaprogramming?

  - by Ivan

  As I've found myself repeating myself a lot, writing very similar queries and classes for different entities (despite of doing strong object and relational normalisation), etc, I've came to an Idea that I could and should automate the most of this and write an engine which will compile simple declarative models I specify into all the code limiting my job to describe the task and and finally just customise the result as needed. As far as I know this is about metaprogramming and aspect-oriented programming. How do I get acquainted with modern tools available quickly so that I don't invent one more bicycle developing my own?

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• Zend without Database

  - by dbemerlin

  Hi, i googled for an hour now but maybe my Google-Fu is just too weak, i couldn't find a solution. I want to create an application that queries a service via JSON requests (all data and backend/business logic is stored in the service). With plain PHP it's simple enough since i just make a curl request, json_decode the result and get what i need. This already works quite well. A request might look like this: Call http://service-host/userlist with body: {"logintoken": "123456-1234-5678-901234"} Get Result: { "status": "Ok", "userlist":[ {"name": "foo", "id": 1}, {"name": "bar", "id": 2} ] } Now we want to get that into the Zend Framework since it's a hobby project and we want to learn about Zend. The problem is that all information i could find use a Database. Is there even a way to create a Zend Project that does not use a Database? And how can i write a model that represents the actions instead of objects and object-relations?

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• How to Sum calulated fields

  - by Nazero Jerry

  I‘d like to ask I question that here that I think would be easy to some people. Ok I have query that return records of two related tables. (One to many) In this query I have about 3 to 4 calculated fields that are based on the fields from the 2 tables. Now I want to have a group by clause for names and sum clause to sum the calculated fields but it ends up in error message saying: “You tried to execute a query that is not part of aggregate function” So I decided to just run the query without the totals *(ie no group by , sum etc,,,) : And then I created another query that totals my previous query. ( i.e. using group by clause for names and sum for calculated fields… no calculation here) This is fine ( I use to do this) but I don’t like having two queries just to get summary total. Is their any other way of doing this in the design view and create only one query?. I would very much appreciate. Thankyou: JM

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• How to flush data in php and disconnect user but keep the script alive

  - by Rodrigo

  This is a trick question, while developing a php+ajax application i felt into some long queries, nothing wrong with them, but they could be done in background. I know that there's a way to just send a reply to user while throwing the real processing to another process by exec(), however it dosen't feels right for me, this might generate exploits and it's not pratical on making it compatible with virtual servers and cross platform. PHP offers the ob_* functions although they help on flushing the cache, but the user will keep connected until the script is running. I'm wondering if there's an alternate to exec to keep a script running after sending data to user and closing connection/thread with apache, or a less "dirty" way to have processing data sent to another script.

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• how do i use MySql ENUM type? (and is it right for a news feed)

  - by Haroldo

  I'm creating a table called news_feed, this will log all the actions a user performs. Lets say I want to store user1234 deleted article412 at midday I then need a table like so timestamp | user_id | subject_type | subject_id | method . there would be 5 potential methods to log, methods = add/edit/delete/update/report and lets say 2 possible subject_type subjects = article/comment I know i could make my own key where 0=add, 1=delete etc etc but this would make my queries cumbersome to use/write as i'd need to keep consulting the key. Is there a MySql type which can read lots of identially values quickly? is this ENUM? how do i use it?!!

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• Group by date range on weeks/months interval

  - by khelll

  I'm using MySQL and I have the following table: | clicks | int | | day | date | I want to be able to generate reports like this, where periods are done in the last 4 weeks: | period | clicks | | 1/7 - 7/5 | 1000 | | 25/6 - 31/7 | .... | | 18/6 - 24/6 | .... | | 12/6 - 18/6 | .... | or in the last 3 months: | period | clicks | | July | .... | | June | .... | | April | .... | Any ideas how to make select queries that can generate the equivalent date range and clicks count?

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• Help Forming An SQL Query That Selects The Max Difference Of Two Fields

  - by Frank

  I'm trying to select a record with the most effective votes. Each record has an id, the number of upvotes (int) and the number of downvotes (int) in a MySQL database. I know basic update, select, insert queries but I'm unsure of how to form a query that looks something like: SELECT * FROM topics WHERE MAX(topic.upvotes - topic.downvotes). Please excuse my made up SQL. The tutorials on SQL I find on the internet cover very basic stuff. Does anyone recommend a good book on this subject?

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• pipelined function

  - by user289429

  Can someone provide an example of how to use parallel table function in oracle pl/sql. We need to run massive queries for 15 years and combine the result. SELECT * FROM Table(TableFunction(cursor(SELECT * FROM year_table))) ...is what we want effectively. The innermost select will give all the years, and the table function will take each year and run massive query and returns a collection. The problem we have is that all years are being fed to one table function itself, we would rather prefer the table function being called in parallel for each of the year. We tried all sort of partitioning by hash and range and it didn't help. Also, can we drop the keyword PIPELINED from the function declaration? because we are not performing any transformation and just need the aggregate of the resultset.

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• Replace repeating character with array elements in PHP

  - by Will Croft

  I hope this is blindingly obvious: I'm looking for the fastest way to replace a repeating element in a string with the elements in a given array, e.g. for SQL queries and parameter replacement. $query = "SELECT * FROM a WHERE b = ? AND c = ?"; $params = array('bee', 'see'); Here I would like to replace the instances of ? with the corresponding ordered array elements, as so: SELECT * FROM a WHERE b = 'bee' and c = 'see' I see that this might be done using preg_replace_callback, but is this the fastest way or am I missing something obvious?

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• Programming languages & proof of concepts

  - by Mike

  There are plenty of programming languages out there, as you all may know. I am primarily looking for a list of programming languages WITH some very neat proof of concepts. I would really like to learn a new language, but whenever I dive into something new and popular, it isn't what I expected. Any tutorial out there will give you code, small examples, but won't show you the true power of the language. I am looking for examples that run entirely on the language that it is exemplifying. For example, If I said C#, I could possibly show you a complete C# app with backend queries, reports, tables, all with a nice interface. It would be completely reliant on the language that is provided, so no supporting languages. I understand that most languages are integrated with other languages in order to provide a richer application. Any links, charts, websites that may reflect this request is appreciated.

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• java jdbc connection to mysql problem

  - by fatnjazzy

  Hi, I am trying to connect to mysql from java web application in eclipse. Connection con = null; try { //DriverManager.registerDriver(new com.mysql.jdbc.Driver()); Class.forName("com.mysql.jdbc.Driver"); con = DriverManager.getConnection("jdbc:mysql://localhost/db_name","root" ,""); if(!con.isClosed()) System.out.println("Successfully connected to " + "MySQL server using TCP/IP..."); } catch(Exception e) { System.err.println("Exception: " + e.getMessage()); } finally { try { if(con != null) con.close(); } catch(SQLException e) { System.out.println(e.toString()); } } I am always getting the Exception: com.mysql.jdbc.Driver I have downloaded this jar http://forums.mysql.com/read.php?39,218287,220327 import it to the "java build path/lib" the mysql version is 5.1.3 under. running: mysql 5.1.3 (db is up and running queries form PHP) windows XP java jee Thanks

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• Building html tables from query data... faster?

  - by Andrew Heath

  With my limited experience/knowledge I am using the following structure to generate HTML tables on the fly from MySQL queries: $c = 0; $t = count($results); $table = '<table>'; while ($c < $t) { $table .= "<tr><td>$results[0]</td><td>$results[1]</td> (etc etc) </tr>"; ++$c; } $table .= '</table>'; this works, obviously. But for tables with 300+ rows there is a noticeable delay in pageload while the script builds the table. Currently the maximum results list is only about 1,100 rows, and the wait isn't long, but there's clearly a wait. Are there other methods for outputting an HTML table that are faster than my WHILE loop? (PHP only please...)

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• Instrumenting Database Access

  - by Whisk

  Jeff mentioned in one of the podcasts that one of the things he always does is put in instrumentation for database calls, so that he can tell what queries are causing slowness etc. This is something I've measured in the past using SQL Profiler, but I'm interested in what strategies other people have used to include this as part of the application. Is it simply a case of including a timer across each database call and logging the result, or is there a 'neater' way of doing it? Maybe there's a framework that does this for you already, or is there a flag I could enable in e.g. Linq-to-SQL that would provide similar functionality. I mainly use c# but would also be interested in seeing methods from different languages, and I'd be more interested in a 'code' way of doing this over a db platform method like SQL Profiler.

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• How to find duplicate values in SQL Server

  - by hgulyan

  Hi, I'm using SQL Server 2008. I have a table Customers customer_number int field1 varchar field2 varchar field3 varchar field4 varchar ... and a lot more columns, that doesn't matter for my queries. Column *customer_number* is pk. I'm trying to find duplicate values and some differences between them. Please, help me to find all rows that have same 1) field1, field2, field3, field4 2) only 3 columns are equal and one of them isn't (except rows from list 1) 3) only 2 columns equal and two of them aren't (except rows from list 1 and list 2) In the end, I'll have 3 tables with this results and additional groupId, which will be same for a group of similars (For example, for 3 column equals, rows that have 3 same columns equal will be a seperate group) Thank you.

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• Complicated conditional SQL query

  - by DevAno1

  I'm not even sure if it's possible but I need it for my Access database. So I have following db structure : Now I need to perform a query that takes category_id from my product and do the magic : - let's say product belongs to console (category_id is in table Console) - from console_types take type_id, where category_id == category_id - but if product belongs to console_game (category_id is in table console_game) - from console_game take game_cat_id, where category_id == category_id I'm not sure if mysql is capable of such thing. If not I'm really f&%ranked up. Maybe there is a way to split this into 2,3 separate queries ?

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• Help with grasping (INNER?) JOIN

  - by Greenie

  I'm having trouble building a query. I can do what I want in 3 different queries. SELECT id FROM table1 WHERE url LIKE '%/$downloadfile' put that in $url_id SELECT item_id FROM table2 WHERE rel_id = '$url_id'" put that in $item_id SELECT rel_id FROM table2 WHERE rel_id = '$item_id' AND field_id = '42'" put that in $user_id But from reading examples on joins and inner joins I think there's a more elegant way. I cant wrap my brain around writing a better query (but would like to) I can describe how it should go: table1 fields: id, url table2 fields item_id, rel_id, field_id I know the last part of table1.url (LIKE '%/$filename') with that I select table1.id. table1.id is equal to one entry in table2.rel_id. So get that and select the table2.item_id. In table2 there is another entry which has the same table2.item_id and it will have a table2.field_id = '42' And finally the value I need is the table2.rel_id where the table2.field_id was 42. I will fetch that value and put it in $user_id Can this be done with one query using joins/inner joins?

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• Is it OK to allow users to query an OLTP SQL Server database with excel?

  - by user169867

  I have a SQL Server 2005 database used by several applications. Some users wish to query the database directly from excel. I can understand this, because it is a useful tool for adhoc queries and then getting the data in a format that's easily transmitted and manipulated by other users. My question is: Does Excel (say 2003/2007) do its querying in a way that won't cause concurency issues? Or is it done in such a way that a seperate datawarehouse database needs to be made to handle this scenario? Thanks for any advise.

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• HBase as web app backend

  - by NathanD

  Can anyone advise if it is a good idea to have HBase as primary data source for web-based application? My primary concern is HBase's response time to queries. Is it possible to have sub-second response? edit: more details about the app itself. Amount of data: ~500GB of text data, expect to reach 1TB soon Number of concurrent users using the app: up to 50 The app will be used to present reports about data stored in HBase, like how many times keyword "X" occured in last 24h. For ~80% of requests from that app I will know the exact key, 20% will be scans (I'm looking into HBase schema design related topics to make it run fast)

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• Ruby implementation of conversion between Latitude/Longitude and OS National Grid Reference point?

  - by Harry Wood

  For converting between Latitude/Longitude and UK's Ordnance Survey National Grid eastings and northings, this seems to be the most popular explanation and reference implementation in JavaScript: http://www.movable-type.co.uk/scripts/latlong-gridref.html The web is littered with other implementations in different languages. Making the conversion via PostGIS queries is another alternative. ...but did anyone implement this maths in ruby? OSGridToLatLong is the direction I'm looking for just at this moment, but I would have thought a library for converting in both directions must surely be available in a gem somewhere. I'm just not searching for the right thing.

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• Can I expect a performance gain from removing this JOIN?

  - by makeee

  I have a "items" table with 1 million rows and a "users" table with 20,000 rows. When I select from the "items" table I do a join on the "users" table (items.user_id = user.id), so that I can grab the "username" from the users table. I'm considering adding a username column to the items table and removing the join. Can I expect a decent performance increase from this? It's already quite fast, but it would be nice to decrease my load (which is pretty high). The downside is that if the user changes their username, items will still reflect their old username, but this is okay with me if I can expect a decent performance increase. I'm asking stackoverflow because benchmarks aren't telling me too much. Both queries finish very quickly. Regardless, I'm wondering if removing the join would lighten load on the database to any significant degree.

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• Best data store for billions of rows

  - by Jody Powlette

  I need to be able to store small bits of data (approximately 50-75 bytes) for billions of records (~3 billion/month for a year). The only requirement is fast inserts and fast lookups for all records with the same GUID and the ability to access the data store from .net. I'm a SQL server guy and I think SQL Server can do this, but with all the talk about BigTable, CouchDB, and other nosql solutions, it's sounding more and more like an alternative to a traditional RDBS may be best due to optimizations for distributed queries and scaling. I tried cassandra and the .net libraries don't currently compile or are all subject to change (along with cassandra itself). I've looked into many nosql data stores available, but can't find one that meets my needs as a robust production-ready platform. If you had to store 36 billion small, flat records so that they're accessible from .net, what would choose and why?

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• lambda expression for a query on two tables that returns records from one table

  - by peetee

  I have two tables TableA (articles) int id int Type string name and TableB (compatibles) int linked_ID int tableA_ID TableA records: id=1, Type=0, name="ArticleA" id=2, Type=1, name="ArticleB" id=3, Type=2, name="ArticleC" id=4, Type=1, name="ArticleD" TableB records: linked_ID= 1, tableA_ID=2 linked_ID= 1, tableA_ID=3 linked_ID= 1, tableA_ID=4 TableB has a list of arcicels that are compatible to a certain article. I am quite new to queries (didn't need them in my projects yet). But as C# and WPF allow some pretty cool automation with Binding I would like to add a binding that returns the following: Give me all articles that are of Type 1 and compatible to my selected article (id=1). The simple part of it works well (articles has a list of all articles): private ObservableCollection<Article> _articles = new ObservableCollection<Article>(); [fill it with the available articles] and then: comboBoxArticles.ItemsSource = _articles.AsBindable().Where( c => c.Typ == 0 ); How can I extend the Where clause to query another table? Thanks a lot in advance.

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• Aggregate functions in ANSI SQL

  - by morpheous

  I want to use multiple aggregate functions in a query. All the examples i have seem on aggregate functions however, are trivial. Typically, they are of the form: SELECT field1,agg_func1, agg_func2 GROUP BY SOME_COLUMNS HAVING agg_func1 OP SOME_SCALAR Where: OP: is a boolean operator (e.g. <, = etc) SOME_SCALAR: is a scalar (i.e. a constant number) What I want to know is if it is possible to write (IN ANSI SQL) queries like: SELECT field1,agg_func1, agg_func2, agg_func3 GROUP BY SOME_COLUMNS HAVING (agg_func1 OP1 agg_func2) OP2 (agg_func2 OP3 agg_func3) Where: OP[N] are boolean operators or ANSI SQL clause operators like 'BETWEEN', 'LIKE', 'IN' etc. Also, assuming this is possible (I have not seen any documentation saying otherwise) are there any efficiency/performance considerations (i.e. penalties) when the HAVING clause consists of a boolean expression combining the output of the aggregate functions - instead of the normal comparison of the output of the aggregate with a constant number (e.g. min('salary') 100 ) - which is often used in the most banal examples involving aggregate functions?

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• Use LINQ to count the number of combinations existing in two lists

  - by Ben McCormack

  I'm trying to create a LINQ query (or queries) that count the total number of occurences of a combinations of items in one list that exist in a different list. For example, take the following lists: CartItems DiscountItems ========= ============= AAA AAA AAA BBB AAA BBB BBB CCC CCC DDD The result of the query operation should be 2 since I can find two combinations of AAA and BBB (from DiscountItems) within the contents of CartItems. My thinking in approaching the query is to join the lists together to shorten CartItems to only include items from DiscountItems. The solution would be to find the CartItem in the resulting query that occurs the least amount of times, thus indicating how many combinations of items exist in CartItems. How can this be done? Here's the query I already have, but it's not working. query results in an enumeration with 100 items, far more than I expected. Dim query = From cartItem In Cart.CartItems Group Join discountItem In DiscountGroup.DiscountItems On cartItem.SKU Equals discountItem.SKU Into Group Select SKU = cartItem.SKU, CartItems = Group Return query.Min(Function(x) x.CartItems.Sum(Function(y) y.Quantity))

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• Proper abstraction of the database tier in a 3 tier system?

  - by Earlz

  Hello, I am creating a 3 tier application. Basically it goes Client - (through optional server to be a thin-client) - Business Logic - Database Layer And basically making it so that there is never any skipping around. As such, I want for all of the SQL queries and such to be in the Database Layer. Well, now I'm a bit confused. I made a few static classes to start off the database tier but what should I do for the database connections? Should I just create a new database connection anytime I enter the Database Layer or would that be wasteful? Does Connection.Open() take time whenever you have a ConnectionPool? To me, it just feels wrong for the Business tier to have to pass in a IdbConnection object to the Database tier. It seems like the Database tier should handle all of that DB-specific code. What do you think? How can I do it the proper way while staying practical?

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