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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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  • is there a tool to see the difference between two database tables in SQL Server?

    - by reinier
    What is a good tool to see the differences between 2 tables (or even better, the datasets returned by 2 queries). EDIT: I'm not interested in the schema changes. Just assume that the schemas are the same. background as to why: I'm porting some legacy code which can fill a database with some pre-calced data. The easiest way to see if I got everything right, is to check the output of the old program, with the new one. I was thinking that if there is some kind of 'diff' tool for databases, this might be great.

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  • Active record taking Date.today as yesterday

    - by Mongus Pong
    I have a strange one.. I am doing something like : tip = find (:first, :conditions => ["last_shown = ? or last_shown is null", Date.today]) And then a little later on I do : tip.last_shown = Date.today tip.save When I look at output of these queries, ActiveRecord is doing the first query with todays date as I would expect. However, the send query, ActiveRecord is setting the last_shown date to be yesterdays date. Why on earth would it do this? I have config.time_zone = 'UTC' in my environment.rb. I can use Time.now.utc.to_date instead of Date.today but it makes no difference.

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  • How important is caching for a site's speed with PHP?

    - by benhowdle89
    I've just made a user-content orientated website http://www.humanisms.co.uk Its done in PHP, MySQL and jQuery's AJAX, at the moment there is only a dozen or so submissions and already i can feel it lagging slightly when it goes to a new page (therefore running a new mysql query) Is it most important for me to try and optimise my mysql queries (by prepared statements) or is it worth in looking at CDN's (amazon s3) and caching (much like the WordPress plugin WP Super Cache) which works by serving static HTML files when there hasnt been new content submitted. Which route is the most beneficial, for me as a developer, to take, ie. where am i better off concentrating my efforts to speed up the site?

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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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  • INET_ATON() and INET_NTOA() in PHP?

    - by blerh
    I want to store IP addresses in my database, but I also need to use them throughout my application. I read about using INET_ATON() and INET_NTOA() in my MySQL queries to get a 32-bit unsigned integer out of an IP address, which is exactly what I want as it will make searching through the database faster than using char(15). The thing is, I can't find a function that does the same sort of thing in PHP. The only thing I came across is: http://php.net/manual/en/function.ip2long.php So I tested it: $ip = $_SERVER['REMOTE_ADDR']; echo ip2long($ip); And it outputs nothing. In the example they gave it seems to work, but then again I'm not exactly sure if ip2long() does the same thing as INET_ATON(). Does someone know a PHP function that will do this? Or even a completely new solution to storing an IP address in a database? Thanks.

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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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  • Linq for two tables

    - by Diana
    I need to do something like this, My two tables have the same signature, but different class so It suppose to work but it is not working. var myTable; if (booleanVariable == true) { myTable = table1; } else { myTable = table2; } var myLinq1 = from p in myTable join r in myOtherTable select p; In this case, I have to initialize myTable I have tried also, var myTablev= table2; if (booleanVariable == true) { myTable = table1; } var myLinq1 = from p in myTable join r in myOtherTable select p; then var is type table2, then it can't be changed to table1 type. I need help, I don't want to make a copy paste of all the code. the linq query is huge, and it s nested with 5 or 6 queries. also I have to do this on 12 different methods. Thanks a lot for your help.

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  • same Linq for two tables

    - by Diana
    I need to do something like this, My two tables have the same signature, but different class so It suppose to work but it is not working. var myTable; if (booleanVariable == true) { myTable = table1; } else { myTable = table2; } var myLinq1 = from p in myTable join r in myOtherTable select p; In this case, I have to initialize myTable I have tried also, var myTable= table2; if (booleanVariable == true) { myTable = table1; } var myLinq1 = from p in myTable join r in myOtherTable select p; then var is type table2, then it can't be changed to table1 type. I need help, I don't want to make a copy paste of all the code. the linq query is huge, and it s nested with 5 or 6 queries. also I have to do this on 12 different methods. Thanks a lot for your help.

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  • Sql query - how to construct

    - by Max Malmgren
    Hi. I am working to implement a dataconnection between my C# application and an Sql Express database. Please bear in mind I have not worked with Sql queries before. I have the following relevant tables: ArticlesCommon ArticlesLocalized CategoryCommon CategoryLocalized where ArticlesCommon holds language independent information such as price, weight etc. This is the statement for now: SELECT * FROM ArticlesCommon INNER JOIN ArticlesLocalized ON ArticlesCommon.ID = ArticlesLocalized.ID WHERE ArticlesLocalized.Language = @language ORDER BY ArticlesCommon.DateAdded ArticlesCommon contains a category id for each row. Now, I want to use this to look up the localized information in CategoryLocalized and add it to the result, something like SELECT *, CategoryLocalized.Name as CategoryName. If I have gotten my point across, is this doable? Thank you.

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  • Microsoft SQL Server 2008 - 99% fragmentation on non-clustered, non-unique index

    - by user550441
    I have a table with several indexes (defined below). One of the indexes (IX_external_guid_3) has 99% fragmentation regardless of rebuilding/reorganizing the index. Anyone have any idea as to what might cause this, or the best way to fix it? We are using Entity Framework 4.0 to query this, the EF queries on the other indexed fields about 10x faster on average then the external_guid_3 field, however an ADO.Net query is roughly the same speed on both (though 2x slower than the EF Query to indexed fields). Table id(PK, int, not null) guid(uniqueidentifier, null, rowguid) external_guid_1(uniqueidentifier, not null) external_guid_2(uniqueidentifier, null) state(varchar(32), null) value(varchar(max), null) infoset(XML(.), null) -- usually 2-4K created_time(datetime, null) updated_time(datetime, null) external_guid_3(uniqueidentifier, not null) FK_id(FK, int, null) locking_guid(uniqueidentifer, null) locked_time(datetime, null) external_guid_4(uniqueidentifier, null) corrected_time(datetime, null) is_add(bit, not null) score(int, null) row_version(timestamp, null) Indexes PK_table(Clustered) IX_created_time(Non-Unique, Non-Clustered) IX_external_guid_1(Non-Unique, Non-Clustered) IX_guid(Non-Unique, Non-Clustered) IX_external_guid_3(Non-Unique, Non-Clustered) IX_state(Non-Unique, Non-Clustered)

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  • nHibernate query by example with multiple associated objects

    - by BurnWithLife
    I'm trying to use nhibernate's query by example to build dynamic queries. I'm stuck on how to code for an example object with multiple associations. Here's an example from NHibernate in Action. Its a User object with Items. Example exampleUser = Example.Create(u).IgnoreCase().EnableLike(MatchMode.Anywhere); Example exampleItem = Example.Create(i).IgnoreCase().EnableLike(MatchMode.Anywhere); return GetSession().CreateCriteria(typeof(User)) .Add( exampleUser ) .CreateCriteria("Items") .Add( exampleItem ) .List<User>(); If the User object has let's say a Category object as a property, how could I add that in to the above example? If i put another CreateCriteria at the end it refers to the Items, not the User.

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  • Need to map classes to different databases at runtime in Hibernate

    - by serg555
    I have MainDB database and unknown number (at compile time) of UserDB_1, ..., UserDB_N databases. MainDB contains names of those UserDB databases in some table (new UserDB can be created at runtime). All UserDB have exactly the same table names and fields. How to handle such situation in Hibernate? (database structure cannot be changed). Currently I am planning to create generic User classes not mapped to anything and just use native SQL for all queries: session.createSQLQuery("select * from " + db + ".user where id=1") .setResultTransformer(Transformers.aliasToBean(User.class)); Is there anything better I can do? Ideally I would want to have mappings for UserDB tables and relations and use HQL on required database.

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  • a quick overview on access

    - by masfenix
    Hey I am a university student (math major), but programming since I was little (read: 14). I am starting a new programming job tomorrow at a very big company. However I just found out that I might be just working with access for a couple of weeks (macros and whatnot). Can someone just give me a general rundown on how to create and use VB in access. What I mean is how do tables refer to themselves (as objects? as what name?) how to run queries through vb and such. thanks all.

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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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  • how to create a subquery in sql using count based on outer query

    - by user1754716
    I hope someone can help me with this query. Basically I have two queries that I want to "combine". I want the second query as an extra column along with the first query. The first one is this : SELECT t_Item_Storage_Location.Storage_Loc_Nbr, t_Storage_Location.Storage_Loc_Type_Code, Count(t_Load.Load_Id) AS CurrentLoadCount, t_load.MMM_Id_Nbr FROM t_Load INNER JOIN (t_Storage_Location INNER JOIN t_Item_Storage_Location ON t_Storage_Location.Storage_Loc_Nbr = t_Item_Storage_Location.Storage_Loc_Nbr) ON (t_Load.Storage_Loc_Nbr = t_Item_Storage_Location.Storage_Loc_Nbr) AND (t_Load.MMM_Id_Nbr = t_Item_Storage_Location.MMM_Id_Nbr) where ((((t_Item_Storage_Location.MMM_Id_Nbr) Between '702004%' And '702011%') AND ((t_Item_Storage_Location.Storage_Loc_Nbr) Like '%A') AND ((t_Storage_Location.Storage_Loc_Type_Code)='CD') AND ((t_Load.Active_Status_Ind)='A') AND ((t_Load.QC_Status_Code) Like 'R%') AND ((t_Load.MMM_Facility_Code)='MC')) OR (((t_Item_Storage_Location.Storage_Loc_Nbr) Like '%B')) OR (((t_Item_Storage_Location.Storage_Loc_Nbr) Like '%C')) OR (((t_Item_Storage_Location.Storage_Loc_Nbr) Like '%D')) OR (((t_Item_Storage_Location.Storage_Loc_Nbr) Like '%E')) ) GROUP BY t_Item_Storage_Location.MMM_Id_Nbr, t_Item_Storage_Location.Storage_Loc_Nbr, t_Storage_Location.Storage_Loc_Type_Code, t_Load.MMM_Facility_Code, t_load.MMM_Id_Nbr HAVING Count(t_Load.Load_Id)<4 The second one, is based on the t_load.MMM_Id_Nbr of the first one. Basically I want a count of all the loads with that mmm_id_nbr. SELECT count(Load_ID) as LoadCount, MMM_Id_Nbr, storage_Loc_Nbr FROM t_load WHERE QC_Status_Code like 'R%' and mmm_Facility_Code ='MC' and Active_Status_Ind='A' GROUP by MMM_Id_Nbr, storage_loc_Nbr

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  • Multiple unrelated in JasperReports

    - by Laren Mortensen
    I am using iReport with JasperReports. I want to include multiple subreports that have unrelated sql queries. I would like to be able to put these all on one report. The problem I am facing is that when I leave the master report sql query empty, none of my subreports have any data. There isn't really anything that the master report sends to the subreports since they are unrelated. Basically how do you throw multiple unrelated reports together into one report.

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  • Most optimal order (of joins) for left join

    - by Ram
    I have 3 tables Table1 (with 1020690 records), Table2(with 289425 records), Table 3(with 83692 records).I have something like this SELECT * FROM Table1 T1 /* OK fine select * is bad when not all columns are needed, this is just an example*/ LEFT JOIN Table2 T2 ON T1.id=T2.id LEFT JOIN Table3 T3 ON T1.id=T3.id and a query like this SELECT * FROM Table1 T1 LEFT JOIN Table3 T3 ON T1.id=T3.id LEFT JOIN Table2 T2 ON T1.id=T2.id The query plan shows me that it uses 2 Merge Join for both the joins. For the first query, the first merge is with T1 and T2 and then with T3. For the second query, the first merge is with T1 and T3 and then with T2. Both these queries take about the same time(40 seconds approx.) or sometimes Query1 takes couple of seconds longer. So my question is, does the join order matter ?

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  • YAGNI and database creation scripts

    - by Daniel Straight
    Right now, I have code which creates the database (just a few CREATE queries on a SQLite database) in my main database access class. This seems unnecessary as I have no intention of ever using the code. I would just need it if something went wrong and I needed to recreate the database. Should I... Leave things as they are, even though the database creation code is about a quarter of my file size. Move the database-creation code to a separate script. It's likely I'll be running it manually if I ever need to run it again anyway, and that would put it out-of-sight-out-of-mind while working on the main code. Delete the database-creation code and rely on revision control if I ever find myself needing it again.

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  • Is an ORM redundant with a NoSQL API?

    - by Earlz
    Hello, with MongoDB (and I assume other NoSQL database APIs worth their salt) the ways of querying the database are much more simplistic than SQL. There is no tedious SQL queries to generate and such. For instance take this from mongodb-csharp: using MongoDB.Driver; Mongo db = new Mongo(); db.Connect(); //Connect to localhost on the default port. Document query = new Document(); query["field1"] = 10; Document result = db["tests"]["reads"].FindOne(query); db.Disconnect(); How could an ORM even simplify that? Is an ORM or other "database abstraction device" required on top of a decent NoSQL API?

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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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  • Accessing database problem

    - by anarche
    Ok, so I've got an SQLiteOpenHelper that prepares and returns a SQLiteDatabase object; this is written singleton-pattern, so the database is opened once and only closed when the Activity closes. From there I have three database wrappers encapsulating the queries (some returning cursors to datasets, some inserting data) used by the Activity. I want to insert data from one View, then have that automatically update in another View on the same Dialogue. I'm writing this on a notepad and testing on the phone (since the emulator crashes the notepad...), so I can't pull up stacktraces atm. So questions: 1) are there limitations to writing to a database, when there are cursors open on the database? 2) Does a Cursor.requery()? call update the ListView with the cursor as a data connector?

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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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  • PHP - Too many mysql_query("SELECT .. ") .. ?

    - by Mike
    Hey, I'm making an e-shop and to display the tree of categories and all the products with their multiple variations of prices I made like more than 150 mysql_query("SELECT ..."); queries on one page. (If I count the "while" loops). Is it too many, and if yes, can it have any negative effect? (ofc. it takes longer to load the data ..) Also can I anyhow achieve the effect of this code without doing it that way? $result2 = mysql_query("SELECT * FROM ceny WHERE produkt_id='$id' ORDER BY gramaz"); $result3 = mysql_query("SELECT * FROM ceny WHERE produkt_id='$id' ORDER BY gramaz"); $result4 = mysql_query("SELECT * FROM ceny WHERE produkt_id='$id' ORDER BY gramaz"); $result5 = mysql_query("SELECT * FROM ceny WHERE produkt_id='$id' ORDER BY gramaz"); while( $row2 = mysql_fetch_array( $result2 )) { } while( $row3 = mysql_fetch_array( $result2 )) { } while( $row4 = mysql_fetch_array( $result2 )) { } while( $row5 = mysql_fetch_array( $result2 )) { } Thanks, Mike.

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  • Update query with conditional?

    - by dmontain
    I'm not sure if this possible. If not, let me know. I have a PDO mysql that updates 3 fields. $update = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2, field3=:field3 WHERE key=:key"); But I want field3 to be updated only when $update3 = true; (meaning that the update of field3 is controlled by a conditional statement) Is this possible to accomplish with a single query? I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. //run this query to update only fields 1 and 2 $update_part1 = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2 WHERE key=:key"); //if field3 should be update, run a separate query to update it separately if ($update3){ $update_part2 = $mypdo->prepare("UPDATE tablename SET field3=:field3 WHERE key=:key"); } But hopefully there is a way to accomplish this in 1 query?

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