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  • LINQ2SQL: how to merge two columns from the same table into a single list

    - by TomL
    this is probably a simple question, but I'm only a beginner so... Suppose I have a table containing home-work locations (cities) certain people use. Something like: ID(int), namePerson(string), homeLocation(string), workLocation(string) where homeLocation and workLocation can both be null. Now I want all the different locations that are used merged into a single list. Something like: var homeLocation = from hm in Places where hm.Home != null select hm.Home; var workLocation = from wk in Places where wk.Work != null select wk.Work; List<string> locationList = new List<string>(); locationList = homeLocation.Distinct().ToList<string>(); locationList.AddRange(workLocation.Distinct().ToList<string>()); (which I guess would still allow duplicates if they have the same value in both columns, which I don't really want...) My question: how this be put into a single LINQ statement? Thanks in advance for your help!

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  • What is the difference between these two LINQ statements?

    - by jamone
    I had the 1nd statement in my code and found it not giving an accurate count, it was returning 1 when the correct answer is 18. To try and debug the problem I broke it out creating the 2nd statement here and the count returns 18. I just don't see what the difference is between these two. It seems like the 1st is just more compact. I'm currently running these two statements back to back and I'm sure that the database isn't changing between the two. int count = (from s in surveysThisQuarter where s.FacilityID == facility.LocationID select s.Deficiencies).Count(); vs var tempSurveys = from s in surveysThisQuarter where s.FacilityID == facility.LocationID select s; int count = 0; foreach (Survey s in tempSurveys) count += s.Deficiencies.Count();

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  • Ways to update a dependent table in the same MySQL transaction?

    - by codie
    I need to update two tables inside a single transaction. The individual queries look something like this: 1. INSERT INTO t1 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = val2; If the above query causes an insert then I need to run the following statement on the second table: 2. INSERT INTO t2 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = col2 + val2; otherwise, 3. UPDATE t2 SET col2 = col2 - old_val2 + val2 WHERE col1 = val1; -- old_val2 is the value of t1.col2 before it was updated Right now I run a SELECT on t1 first, to determine whether statement 1 will cause an insert or update on t1. Then I run statement 1 and either of 2 and 3 inside a transaction. What are the ways in which I can do all of these inside one transaction itself? The approach I was thinking of is the following: UPDATE t2, t1 set t2.col2 = t2.col2 - t1.col2 WHERE t1.col1 = t2.col2 and t1.col1 = val1; INSERT INTO t1 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = val2; INSERT INTO t2, t1 (t2.col1, t2.col2) VALUES (t1.col1, t1.col2) ON DUPLICATE KEY UPDATE t2.col2 = t2.col2 + t1.col2 WHERE t1.col1 = t2.col2 and t1.col1 = val1; Unfortunately, there's no multi-table INSERT... ON DUPLICATE KEY UPDATE in MySQL 5.0. What else could I do?

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  • How to SELECT DISTINCT Info with TOP 1 Info and an Order By FROM the Top 1 Info

    - by Erin Taylor
    I have 2 tables, that look like: CustomerInfo(CustomterID, CustomerName) CustomerReviews(ReviewID, CustomerID, Review, Score) I want to search reviews for a string and return CustomerInfo.CustomerID and CustomerInfo.CustomerName. However, I only want to show distinct CustomerID and CustomerName along with just one of their CustomerReviews.Reviews and CustomerReviews.Score. I also want to order by the CustomerReviews.Score. I can't figure out how to do this, since a customer can leave multiple reviews, but I only want a list of customers with their highest scored review. Any ideas?

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  • Single Query returning me 4 tables, How to get all of them back into dataset ?

    - by Shantanu Gupta
    How to fill multiple tables in a dataset. I m using a query that returns me four tables. At the frontend I am trying to fill all the four resultant table into dataset. Here is my Query. Query is not complete. But it is just a refrence for my Ques Select * from tblxyz compute sum(col1) suppose this query returns more than one table, I want to fill all the tables into my dataset I am filling result like this con.open(); adp.fill(dset); con.close(); Now when i checks this dataset. It shows me that it has four tables but only first table data is being displayed into it. rest 3 dont even have schema also. What i need to do to get desired output

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  • Oracle query to select rows with unique code

    - by Jasim
    I have a table like this C1 C2 C3 Code 1 2 3 33 1 2 3 34 2 4 1 14 1 2 3 14 i want to select only those record whose code is appearing only in single row. ie, in this case rows with code 33 and 34.. as they appear only once in this table. How can i write a query for that

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  • Scalable Database Tagging Schema

    - by Longpoke
    EDIT: To people building tagging systems. Don't read this. It is not what you are looking for. I asked this when I wasn't aware that RDBMS all have their own optimization methods, just use a simple many to many scheme. I have a posting system that has millions of posts. Each post can have an infinite number of tags associated with it. Users can create tags which have notes, date created, owner, etc. A tag is almost like a post itself, because people can post notes about the tag. Each tag association has an owner and date, so we can see who added the tag and when. My question is how can I implement this? It has to be fast searching posts by tag, or tags by post. Also, users can add tags to posts by typing the name into a field, kind of like the google search bar, it has to fill in the rest of the tag name for you. I have 3 solutions at the moment, but not sure which is the best, or if there is a better way. Note that I'm not showing the layout of notes since it will be trivial once I get a proper solution for tags. Method 1. Linked list tagId in post points to a linked list in tag_assoc, the application must traverse the list until flink=0 post: id, content, ownerId, date, tagId, notesId tag_assoc: id, tagId, ownerId, flink tag: id, name, notesId Method 2. Denormalization tags is simply a VARCHAR or TEXT field containing a tab delimited array of tagId:ownerId. It cannot be a fixed size. post: id, content, ownerId, date, tags, notesId tag: id, name, notesId Method 3. Toxi (from: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html, also same thing here: http://stackoverflow.com/questions/20856/how-do-you-recommend-implementing-tags-or-tagging) post: id, content, ownerId, date, notesId tag_assoc: ownerId, tagId, postId tag: id, name, notesId Method 3 raises the question, how fast will it be to iterate through every single row in tag_assoc? Methods 1 and 2 should be fast for returning tags by post, but for posts by tag, another lookup table must be made. The last thing I have to worry about is optimizing searching tags by name, I have not worked that out yet. I made an ASCII diagram here: http://pastebin.com/f1c4e0e53

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  • How to Generate XML from Database

    - by Nisarg Mehta
    Hi , I am fetching data from two tables CARRIER_IFTA ,IFTA_NAME. My Select Query is like below.. SELECT t1.IFTA_LICENSE_NUMBER,t1.IFTA_BASE_STATE,t2.NAME_TYPE,t2.NAME from CARRIER_IFTA t1 inner join IFTA_NAME t2 on t1.IFTA_LICENSE_NUMBER=t2.IFTA_LICENSE_NUMBER My Data is coming in this way... IFTA_LICENSE_NUMBER IFTA_BASE_STATE NAME_TYPE NAME -------------------------------------------------------- 630908333 US LG XYZ 630908333 US MG PQR 730908344 US LG ABC Now using XSLT I want to generate XML like this <T0019> <IFTA_ACCOUNT> <IFTA_LICENSE_NUMBER>630908333</IFTA_LICENSE_NUMBER> <IFTA_BASE_STATE>US</IFTA_BASE_STATE> <IFTA_NAME> <NAME_TYPE>LG<NAME_TYPE> <NAME>XYZ</NAME> </IFTA_NAME> <IFTA_NAME> <NAME_TYPE>MG<NAME_TYPE> <NAME>PQR</NAME> <IFTA_NAME> </IFTA_ACCOUNT> <IFTA_ACCOUNT> <IFTA_LICENSE_NUMBER>730908344</IFTA_LICENSE_NUMBER> <IFTA_BASE_STATE>US</IFTA_BASE_STATE> <IFTA_NAME> <NAME_TYPE>LG<NAME_TYPE> <NAME>ABC</NAME> </IFTA_NAME> </IFTA_ACCOUNT> </T0019> i have used below xslt but it is not giveng me desire result ... <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0"> <xsl:template match="/ROWSET"> <xsl:element name="T0019"> <xsl:apply-templates select="IFTAACCOUNT"/> </xsl:element> </xsl:template> <xsl:template match="IFTAACCOUNT"> <xsl:element name="IFTAACCOUNT"> <xsl:apply-templates select="IFTA_CARRIER_ID_NUMBER"/> </xsl:element> </xsl:template> <xsl:template match="IFTA_LICENSE_NUMBER"> <xsl:element name="IFTA_LICENSE_NUMBER"> <xsl:apply-templates /> </xsl:element> </xsl:template> <xsl:template match="IFTA_BASE_STATE"> <xsl:element name="IFTA_BASE_STATE"> <xsl:apply-templates /> </xsl:element> </xsl:template> <xsl:template match="IRP_NAME"> <IRP_NAME> <xsl:apply-templates select="NAME"/> <xsl:apply-templates select="NAME_TYPE"/> </IRP_NAME> </xsl:template> <xsl:template match="NAME"> <xsl:element name="NAME"> <xsl:value-of select="." /> </xsl:element> </xsl:template> <xsl:template match="NAME_TYPE"> <xsl:element name="NAME_TYPE"> <xsl:apply-templates /> </xsl:element> </xsl:template> </xsl:stylesheet> but it is not giving desire result ... Please help me ... Thanks in Advance...

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  • Looking for books

    - by robblot
    When I was learning Visual Basic.net 2008 I found a book that not only taught the basics but by the end of the book I had developed a fully working database application. Does anyone know where I might find a simular book but using Visual C++?

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  • Storing users in a database

    - by EMcKenna
    Im wondering whats the best way of storing different types of users in my database. I am writing an application that has 4 main user types (admin, school, teacher, student). At the moment I have a table for each of these but i'm not sure thats the best way of storing user information. For instance... Allowing students to PM other student is simple (store sender and receiver student_id) but enabling teachers to PM students requires another table (sender teacher_id, sender student_id). Should all users be stored in one users table with a user_type field? If so, the teacher / student specific information will still have to be stored in another table. users user_id, password_hash, user_type students user_id, student_specific_stuff... teachers user_id, teacher_specific_stuff... How do I stop a user who has a user_type = student from being accidentally being entered into the teachers table (as both have a user_id) Just want to make sure I get the database correct before i go any further. Thanks...

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  • How can I join on a CSV varchar?

    - by mgroves
    I have a varchar field that contains a string like "10,11,12,13". How can I use that CSV string to join to another table with those IDs? Here's the approach I'm taking now: select * from SomeTable a WHERE (',' + @csvString + ',') LIKE '%,' + CONVERT(varchar(25), a.ID) + ',%' Where @csvString is "10,11,12,...". I intend to use this method as a join condition as well. That method works, but it's rather slow (using CAST doesn't improve the speed). I understand that having CSVs in the database like that is usually a very silly idea in most cases, but there's nothing I can do about that.

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  • Nested query to find details in table B for maximum value in table A

    - by jpatokal
    I've got a huge bunch of flights travelling between airports. Each airport has an ID and (x,y) coordinates. For a given list of flights, I want to find the northernmost (highest x) airport visited. Here's the query I'm currently using: SELECT name,iata,icao,apid,x,y FROM airports WHERE y=(SELECT MAX(y) FROM airports AS a , flights AS f WHERE (f.src_apid=a.apid OR f.dst_apid=a.apid) ) This works beautifully and reasonably fast as long as y is unique, but fails once it isn't. What I'd want to do instead is find the MAX(y) in the subquery, but return the unique apid for the airport with the highest y. Any suggestions?

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  • Extract multiple values from one column in MySql

    - by Neil
    I've noticed that MySql has an extensive search capacity, allowing both wildcards and regular expressions. However, I'm in somewhat in a bind since I'm trying to extract multiple values from a single string in my select query. For example, if I had the text "<span>Test</span> this <span>query</span>", perhaps using regular expressions I could find and extract values "Test" or "query", but in my case, I have potentially n such strings to extract. And since I can't define n columns in my select statement, that means I'm stuck. Is there anyway I could have a list of values (ideally separated by commas) of any text contained with span tags? In other words, if I ran this query, I would get "Test,query" as the value of spanlist: select <insert logic here> as spanlist from HtmlPages ...

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  • SqlCE DB occasionally freezes on one handheld, not another

    - by Michael
    I have two types of custom handhelds which are similar, but slightly different, each running the same WinForm application and a WinCE database: Type 1: WinCE 4.2, 400 mhz, 93244 kb Type 2: WinCE 5.0, 520 mhz, 84208 kb Type 1 will happily proceed through a large batch db operation (initiated) by the app, by Type 2 will consistently begin c-r-a-w-l-i-n-g (for several to many cycles) at around the 200 cycle mark. As several points it will begin running normally and then crawl again. The app does several db op's (inserts, updates and selects, no deletes). To simplify my situation, I've built a small test app which essentially does this: command_s.CommandText = "select dvr from vr where vid = 2211250"; command_u.CommandText = "update pvr set LocationID=81 where Status='OK' and vri = 27861"; while(going) { command_s.ExecuteScalar(); command_u.ExecuteNonQuery(); } and set it off running on the two units side by side. Sure enough, the slower (400 mhz) unit is outpacing the faster (520 mhz) unit (it's about 5000 cycles ahead right now) and I can see noticable pauses on the 520 mhz unit. What is causing this?

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  • How to secure the communication between an MSSQL database and a c# administrative tool?

    - by citronas
    How can I secure the communication between a C# programm running locally on my computer and a MSSQL Server in a hosted environment? I have an asp.net application that is secured by SSL encryption. So using the asp.net from an open wlan connection is no problem. How can I achieve the same kind of encryption for my administrative tool? Would it be best to write a service? But how would that connection to the service be secured?

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  • rails include with options

    - by holden
    Is it possible to limit an AR :include to say only pull in one record... Item.find(:all, :include => [ :external_ratings, :photos => LIMIT 1 ]) I have a list of items and each item has between 5 and 15 photos. I want to load a photo id into memory, but i don't need all of them, I just want to preview the first one. Is there a way to do this?

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  • Add LINQ Auto-Generated Value Marker [Column(IsDbGenerated=true)] in Buddy Class

    - by Alex
    Hello, is it possible to decorate a field of a LINQ generated class with [Column(IsDbGenerated=true)] using a buddy class (which is linked to the LINQ class via [MetadataType(typeof(BuddyMetadata))]) ? My goal is to be able to clear and repopulate the LINQ ORM designer without having to set the "Auto Generate Value" property manually every time to re-establish the fact that certain columns are autogenerated. Thanks!

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  • Mysql - help me optimize this query (improved question)

    - by sandeepan-nath
    About the system: - There are tutors who create classes and packs - A tags based search approach is being followed.Tag relations are created when new tutors register and when tutors create packs (this makes tutors and packs searcheable). For details please check the section How tags work in this system? below. Following is the concerned query SELECT SUM(DISTINCT( t.tag LIKE "%Dictatorship%" )) AS key_1_total_matches, SUM(DISTINCT( t.tag LIKE "%democracy%" )) AS key_2_total_matches, COUNT(DISTINCT( od.id_od )) AS tutor_popularity, CASE WHEN ( IF(( wc.id_wc > 0 ), ( wc.wc_api_status = 1 AND wc.wc_type = 0 AND wc.class_date > '2010-06-01 22:00:56' AND wccp.status = 1 AND ( wccp.country_code = 'IE' OR wccp.country_code IN ( 'INT' ) ) ), 0) ) THEN 1 ELSE 0 END AS 'classes_published', CASE WHEN ( IF(( lp.id_lp > 0 ), ( lp.id_status = 1 AND lp.published = 1 AND lpcp.status = 1 AND ( lpcp.country_code = 'IE' OR lpcp.country_code IN ( 'INT' ) ) ), 0) ) THEN 1 ELSE 0 END AS 'packs_published', td . *, u . * FROM tutor_details AS td JOIN users AS u ON u.id_user = td.id_user LEFT JOIN learning_packs_tag_relations AS lptagrels ON td.id_tutor = lptagrels.id_tutor LEFT JOIN learning_packs AS lp ON lptagrels.id_lp = lp.id_lp LEFT JOIN learning_packs_categories AS lpc ON lpc.id_lp_cat = lp.id_lp_cat LEFT JOIN learning_packs_categories AS lpcp ON lpcp.id_lp_cat = lpc.id_parent LEFT JOIN learning_pack_content AS lpct ON ( lp.id_lp = lpct.id_lp ) LEFT JOIN webclasses_tag_relations AS wtagrels ON td.id_tutor = wtagrels.id_tutor LEFT JOIN webclasses AS wc ON wtagrels.id_wc = wc.id_wc LEFT JOIN learning_packs_categories AS wcc ON wcc.id_lp_cat = wc.id_wp_cat LEFT JOIN learning_packs_categories AS wccp ON wccp.id_lp_cat = wcc.id_parent LEFT JOIN order_details AS od ON td.id_tutor = od.id_author LEFT JOIN orders AS o ON od.id_order = o.id_order LEFT JOIN tutors_tag_relations AS ttagrels ON td.id_tutor = ttagrels.id_tutor JOIN tags AS t ON ( t.id_tag = ttagrels.id_tag ) OR ( t.id_tag = lptagrels.id_tag ) OR ( t.id_tag = wtagrels.id_tag ) WHERE ( u.country = 'IE' OR u.country IN ( 'INT' ) ) AND CASE WHEN ( ( t.id_tag = lptagrels.id_tag ) AND ( lp.id_lp 0 ) ) THEN lp.id_status = 1 AND lp.published = 1 AND lpcp.status = 1 AND ( lpcp.country_code = 'IE' OR lpcp.country_code IN ( 'INT' ) ) ELSE 1 END AND CASE WHEN ( ( t.id_tag = wtagrels.id_tag ) AND ( wc.id_wc 0 ) ) THEN wc.wc_api_status = 1 AND wc.wc_type = 0 AND wc.class_date '2010-06-01 22:00:56' AND wccp.status = 1 AND ( wccp.country_code = 'IE' OR wccp.country_code IN ( 'INT' ) ) ELSE 1 END AND CASE WHEN ( od.id_od 0 ) THEN od.id_author = td.id_tutor AND o.order_status = 'paid' AND CASE WHEN ( od.id_wc 0 ) THEN od.can_attend_class = 1 ELSE 1 END ELSE 1 END GROUP BY td.id_tutor HAVING key_1_total_matches = 1 AND key_2_total_matches = 1 ORDER BY tutor_popularity DESC, u.surname ASC, u.name ASC LIMIT 0, 20 The problem The results returned by the above query are correct (AND logic working as per expectation), but the time taken by the query rises alarmingly for heavier data and for the current data I have it is like 25 seconds as against normal query timings of the order of 0.005 - 0.0002 seconds, which makes it totally unusable. It is possible that some of the delay is being caused because all the possible fields have not yet been indexed. The tag field of tags table is indexed. Is there something faulty with the query? What can be the reason behind 20+ seconds of execution time? How tags work in this system? When a tutor registers, tags are entered and tag relations are created with respect to tutor's details like name, surname etc. When a Tutors create packs, again tags are entered and tag relations are created with respect to pack's details like pack name, description etc. tag relations for tutors stored in tutors_tag_relations and those for packs stored in learning_packs_tag_relations. All individual tags are stored in tags table. The explain query output:- Please see this screenshot - http://www.test.examvillage.com/Explain_query.jpg

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  • validate linqtosql mapping to a model

    - by Coppermill
    I have generated a LinqtoSQL mapping xml file, which I have a valid XSD schema that I check to make sure the XML is correct. Now I want to check that the field type match the Model/Interface for example: checking that the nullable fields are nullable that int are int etc anyone got any ideas if I can do this?

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