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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Database Design Question

    - by deniz
    Hi, I am designing a database for a project. I have a table that has 10 columns, most of them are used whenever the table is accessed, and I need to add 3 more rows; View Count Thumbs Up (count) Thumbs Down (Count) which will be used on %90 of the queries when the table is accessed. So, my question is that whether it is better to break the table up and create new table which will have these 3 columns + Foreign ID, or just make it 13 columns and use no joins? Since these columns will be used frequently, I guess adding 3 more columns is better, but if I need to create 10 more columns which will be used %90 of the time, should I add them as well, or create a new table and use joins? I am not sure when to break the table if the columns are used very frequently. Do you have any suggestions? Thanks 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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  • 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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  • Embedded MongoDB when running integration tests

    - by seanhodges
    My question is a variation of this one. Since my Java Web-app project requires a lot of read filters/queries and interfaces with tools like GridFS, I'm struggling to think of a sensible way to simulate MongoDB in the way the above solution suggests. Therefore, I'm considering running an embedded instance of MongoDB alongside my integration tests. I'd like it to start up automatically (either for each test or the whole suite), flush the database for every test, and shut down at the end. These tests might be run on development machines as well as the CI server, so my solution will also need to be portable. Can anyone with more knowledge on MongoDB help me get idea of the feasibility of this approach, and/or perhaps suggest any reading material that might help me get started? I'm also open to other suggestions people might have on how I could approach this problem...

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  • HQL updates and domain objects

    - by CaptainAwesomePants
    I have what may be a pretty elementary Hibernate question. Do HQL (and/or Criteria) update queries cause updates to live domain objects? And do they automatically flush now-invalid domain objects from the first-level cache? Example: Player playerReference1 = session.get(Player.class,1); session.createQuery("update players set gold = 100").executeUpdate(); //Question #1 -- does playerReference1.getGold() now return 100? Player playerReference2 = session.get(Player.class,1); //Question #2 -- does playerReference2.getGold() return 100, or is it the same exact object? Should I make a practice of evicting all objects that are affected by an HQL update if there's a chance some code will need it later?

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  • Storing search result for paging and sorting

    - by Mattias
    I've been implementing MS Search Server 2010 and so far its really good. Im doing the search queries via their web service, but due to the inconsistent results, im thinking about caching the result instead. The site is a small intranet (500 employees), so it shouldnt be any problems, but im curious what approach you would take if it was a bigger site. I've googled abit, but havent really come over anything specific. So, a few questions: What other approaches are there? And why are they better? How much does it cost to store a dataview of 400-500 rows? What sizes are feasible? Other points you should take into consideration. Any input is welcome :)

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  • Why don't Domain class static methods work from inside a grails "service"?

    - by ?????
    I want a grails service to be able to access Domain static methods, for queries, etc. For example, in a controller, I can call IncomingCall.count() to get the number of records in table "IncomingCall" but if I try to do this from inside a service, I get the error: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'incomingStatusService': Invocation of init method failed; nested exception is groovy.lang.MissingMethodException: No signature of method: static ms.wdw.tropocontrol.IncomingCall.count() is applicable for argument types: () values: [] How do these methods get injected? There's no magic def statement in a controller that appears to do this. Or is the problem that Hibernate isn't available from my Service class?

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  • LINQ to Entity, joining on NOT IN tables

    - by SlackerCoder
    My brain seems to be mush right now! I am using LINQ to Entity, and I need to get some data from one table that does NOT exist in another table. For example: I need the groupID, groupname and groupnumber from TABLE A where they do not exist in TABLE B. The groupID will exist in TABLE B, along with other relevant information. The tables do not have any relationship. In SQL it would be quite simply (there is a more elegant and efficient solution, but I want to paint a picture of what I need) SELECT GroupID, GroupName, GroupNumber, FROM TableA WHERE GroupID NOT IN (SELECT GroupID FROM TableB) Is there an easy/elegant way to do this? Right now I have a bunch of queries hitting the db, then comparing, etc. It's pretty messy. Thanks.

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  • Favoriting system on Appengine

    - by Mateusz Cieslak
    Hi, I have the following model structure class Authors(db.Model) : nickname = db.StringProperty(required=True) fullname = db.StringProperty(required=True) class Articles(db.Model) : title = db.StringProperty(required=True) body = db.StringProperty(required=True) author = db.ReferenceProperty(Authors, required=True) class Favorites(db.Model) : who = db.ReferenceProperty(Authors, required=True) what = db.ReferenceProperty(Articles, required=True) I'd like to display 10 last articles according to this pattern: article.title, article.body, article.author(nickname), info if this article has been already favorited by the signed in user. I have added a function which I use to get the authors of these articles using only one query (it is described here) But I don't know what to do with the favorites (I'd like to know which of the displayed articles have been favorited by me using less than 10 queries (I want to display 10 articles)). Is it possible?

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  • Mysql - multiple values and between

    - by realshadow
    Hey, I need to select 10 products and display them. Each product has 3 different prices. The select to get the prices looks like this: SELECT * FROM products_loans WHERE CODE IN('10X15/12', '10X15/Q10-10', '10X15/Q20-10') AND 550 BETWEEN PRICE_FROM AND PRICE_TO; Where 550 is the base price. Now this select returns 3 rows, but I want to modify it so it will return 30 results. I dont like the idea to execute 10 queries at once. I know I can easily achieve that with "OR", but I would like to ask if there is some other more elegant way to this. The select "should" look like this: SELECT * FROM products_loans WHERE KOD IN('10X15/12', '10X15/Q10-10', '10X15/Q20-10') AND (550, 325, 780) BETWEEN CENA_OD AND CENA_DO; Note that there is no "price" column or anything in the table which I could use to do a JOIN and I cant modify the table.

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  • Oracle (Old?) Joins

    - by Grasper
    I have been porting oracle selects, and I have been running across a lot of queries like so: SELECT e.last_name, d.department_name FROM employees e, departments d WHERE e.department_id(+) = d.department_id; ...and: SELECT last_name, d.department_id FROM employees e, departments d WHERE e.department_id = d.department_id(+); Are there any guides/tutorials for converting all of the variants of the (+) syntax? What is that syntax even called (so I can scour google)? When was this standard phased out? Any info is appreciated.

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  • Why does SQLAlchemy with psycopg2 use_native_unicode have poor performance?

    - by Bob Dover
    I'm having a difficult time figuring out why a simple SELECT query is taking such a long time with sqlalchemy using raw SQL (I'm getting 14600 rows/sec, but when running the same query through psycopg2 without sqlalchemy, I'm getting 38421 rows/sec). After some poking around, I realized that toggling sqlalchemy's use_native_unicode parameter in the create_engine call actually makes a huge difference. This query takes 0.5secs to retrieve 7300 rows: from sqlalchemy import create_engine engine = create_engine("postgresql+psycopg2://localhost...", use_native_unicode=True) r = engine.execute("SELECT * FROM logtable") fetched_results = r.fetchall() This query takes 0.19secs to retrieve the same 7300 rows: engine = create_engine("postgresql+psycopg2://localhost...", use_native_unicode=False) r = engine.execute("SELECT * FROM logtable") fetched_results = r.fetchall() The only difference between the 2 queries is use_native_unicode. But sqlalchemy's own docs state that it is better to keep use_native_unicode=True (http://docs.sqlalchemy.org/en/latest/dialects/postgresql.html). Does anyone know why use_native_unicode is making such a big performance difference? And what are the ramifications of turning off use_native_unicode?

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