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  • Linq2Sql Best Practices

    - by this. __curious_geek
    I'm recently migrating to Linq2Sql and all my future projects will be using Linq2Sql. Having said that, I researched a lot on how to properly plug-in Linq2Sql in application design. what to put at what layer ? How do you design your repositories and business layer services ? Should I use DTOs over Linq2Sql entities on interaction layer ? what things should I be careful about ? what problems did you face ? I did not find any rock-solid material that really talked about one single thing and everyone have their own opinions. I'm looking forward to your ideas on how to integrate/use Linq2Sql in projects. My priority is maintenance[it should be maintenable and when multiple people work on same project] and scalabilty [it should have scope of evolution]. Thanks.

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  • Using 'in' in Join

    - by Ruslan
    i have two selects a & b and i join them like: select * from ( select n.id_b || ',' || s.id_b ids, n.name, s.surname from names n, surnames s where n.id_a = s.id_a ) a left join ( select sn.id, sn.second_name ) b on b.id in (a.ids) in this case join doesn't work :( The problem is in b.id in (a.ids). But why if it looks like 12 in (12,24) and no result :(

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  • Why does this MySQL function return null?

    - by Shore
    Description: the query actually run have 4 results returned,as can be see from below, what I did is just concate the items then return, but unexpectedly,it's null. I think the code is self-explanatory: DELIMITER | DROP FUNCTION IF EXISTS get_idiscussion_ask| CREATE FUNCTION get_idiscussion_ask(iask_id INT UNSIGNED) RETURNS TEXT DETERMINISTIC BEGIN DECLARE done INT DEFAULT 0; DECLARE body varchar(600); DECLARE created DATETIME; DECLARE anonymous TINYINT(1); DECLARE screen_name varchar(64); DECLARE result TEXT; DECLARE cur1 CURSOR FOR SELECT body,created,anonymous,screen_name from idiscussion left join users on idiscussion.uid=users.id where idiscussion.iask_id=iask_id; DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1; SET result = ''; OPEN cur1; REPEAT FETCH cur1 INTO body, created, anonymous, screen_name; SET result = CONCAT(result,'<comment><body><![CDATA[',body,']]></body>','<replier>',if(screen_name is not null and !anonymous,screen_name,''),'</replier>','<created>',created,'</created></comment>'); UNTIL done END REPEAT; CLOSE cur1; RETURN result; END | DELIMITER ; mysql> DELIMITER ; mysql> select get_idiscussion_ask(1); +------------------------+ | get_idiscussion_ask(1) | +------------------------+ | NULL | +------------------------+ 1 row in set (0.01 sec) mysql> SELECT body,created,anonymous,screen_name from idiscussion left join users on idiscussion.uid=users.id where idiscussion.iask_id=1; +------+---------------------+-----------+-------------+ | body | created | anonymous | screen_name | +------+---------------------+-----------+-------------+ | haha | 2009-05-27 04:57:51 | 0 | NULL | | haha | 2009-05-27 04:57:52 | 0 | NULL | | haha | 2009-05-27 04:57:52 | 0 | NULL | | haha | 2009-05-27 04:57:53 | 0 | NULL | +------+---------------------+-----------+-------------+ 4 rows in set (0.00 sec) For those who don't think the code is self-explanatory: Why the function returns NULL?

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  • How to get top 3 frequencies in MySQL?

    - by Amenhotep
    Hello, In MySQL I have a table called "meanings" with three columns: "person" (int), "word" (byte, 16 possible values) "meaning" (byte, 26 possible values). A person assigns one or more meanings to each word: person word meaning ------------------- 1 1 4 1 2 19 1 2 7 <-- second meaning for word 2 1 3 5 ... 1 16 2 Then another person, and so on. There will be thousands of persons. I need to find for each of the 16 words the top three meanings (with their frequencies). Something like: word 1: meaning 5 (35% of people), meaning 19 (22% of people), meaning 2 (13% of people) word 2: meaning 8 (57%), meaning 1 (18%), meaning 22 (7%) ... Is it possible to solve this with a single MySQL query? (If this problem is a classic one and has been answered elsewhere, I would appreciate if you could give me a link to the solution.) Thank you very much, ve

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  • Building Stored Procedure to group data into ranges with roughly equal results in each bucket

    - by Len
    I am trying to build one procedure to take a large amount of data and create 5 range buckets to display the data. the buckets ranges will have to be set according to the results. Here is my existing SP GO /****** Object: StoredProcedure [dbo].[sp_GetRangeCounts] Script Date: 03/28/2010 19:50:45 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO ALTER PROCEDURE [dbo].[sp_GetRangeCounts] @idMenu int AS declare @myMin decimal(19,2), @myMax decimal(19,2), @myDif decimal(19,2), @range1 decimal(19,2), @range2 decimal(19,2), @range3 decimal(19,2), @range4 decimal(19,2), @range5 decimal(19,2), @range6 decimal(19,2) SELECT @myMin=Min(modelpropvalue), @myMax=Max(modelpropvalue) FROM xmodelpropertyvalues where modelPropUnitDescriptionID=@idMenu set @myDif=(@myMax-@myMin)/5 set @range1=@myMin set @range2=@myMin+@myDif set @range3=@range2+@myDif set @range4=@range3+@myDif set @range5=@range4+@myDif set @range6=@range5+@myDif select @myMin,@myMax,@myDif,@range1,@range2,@range3,@range4,@range5,@range6 select t.range as myRange, count(*) as myCount from ( select case when modelpropvalue between @range1 and @range2 then 'range1' when modelpropvalue between @range2 and @range3 then 'range2' when modelpropvalue between @range3 and @range4 then 'range3' when modelpropvalue between @range4 and @range5 then 'range4' when modelpropvalue between @range5 and @range6 then 'range5' end as range from xmodelpropertyvalues where modelpropunitDescriptionID=@idmenu) t group by t.range order by t.range This calculates the min and max value from my table, works out the difference between the two and creates 5 buckets. The problem is that if there are a small amount of very high (or very low) values then the buckets will appear very distorted - as in these results... range1 2806 range2 296 range3 75 range5 1 Basically I want to rebuild the SP so it creates buckets with equal amounts of results in each. I have played around with some of the following approaches without quite nailing it... SELECT modelpropvalue, NTILE(5) OVER (ORDER BY modelpropvalue) FROM xmodelpropertyvalues - this creates a new column with either 1,2,3,4 or 5 in it ROW_NUMBER()OVER (ORDER BY modelpropvalue) between @range1 and @range2 ROW_NUMBER()OVER (ORDER BY modelpropvalue) between @range2 and @range3 or maybe i could allocate every record a row number then divide into ranges from this?

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  • Better way to do SELECT with GROUP BY

    - by Luca Romagnoli
    Hi i've wrote a query that works: SELECT `comments`.* FROM `comments` RIGHT JOIN (SELECT MAX( id ) AS id, core_id, topic_id FROM comments GROUP BY core_id, topic_id order by id desc) comm ON comm.id = comments.id LIMIT 10 I want know if it is possible (and how) to rewrite it to get better performance. Thanks

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  • Adding a computed column to an ActiveRecord query

    - by bmwbzz
    Hi, I am running a query using a scope and some conditions. Something like this: conditions[:offset] = (options[:page].to_i - 1) * PAGE_SIZE unless options[:page].blank? conditions[:limit] = options[:limit] ||= PAGE_SIZE scope = Promo.enabled.active results = scope.all conditions I'd like to add a computed column to the query (at the point when I'm now calling scope.all). Something like this: (ACOS(least(1,COS(0.71106459055501)*COS(-1.2915436464758)*COS(RADIANS(addresses.lat))*COS(RADIANS(addresses.lng))+ COS(0.71106459055501)*SIN(-1.2915436464758)*COS(RADIANS(addresses.lat))*SIN(RADIANS(addresses.lng))+ SIN(0.71106459055501)*SIN(RADIANS(addresses.lat))))*3963.19) as accurate_distance Is there a way to do that without just using find_by_sql and rewriting the whole existing query? Thanks!

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  • Django: Grouping by Dates and Servers

    - by TheLizardKing
    So I am trying to emulate google app's status page: http://www.google.com/appsstatus#hl=en but for backups for our own servers. Instead of service names on the left it'll be server names but the dates and hopefully the pagination will be there too. My models look incredibly similar to this: from django.db import models STATUS_CHOICES = ( ('UN', 'Unknown'), ('NI', 'No Issue'), ('IS', 'Issue'), ('NR', 'Not Running'), ) class Server(models.Model): name = models.CharField(max_length=32) def __unicode__(self): return self.name class Backup(models.Model): server = models.ForeignKey(Server) created = models.DateField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) status = models.CharField(max_length=2, choices=STATUS_CHOICES, default='UN') issue = models.TextField(blank=True) def __unicode__(self): return u'%s: %s' % (self.server, self.get_status_display()) My issue is that I am having a hell of a time displaying the information I need. Everyday a little after midnight a cron job will run and add a row for each server for that day, defaulting on status unknown (UN). My backups.html: {% extends "base.html" %} {% block content %} <table> <tr> <th>Name</th> {% for server in servers %} <th>{{ created }}</th> </tr> <tr> <td>{{ server.name }}</td> {% for backup in server.backup_set.all %} <td>{{ backup.get_status_display }}</td> {% endfor %} </tr> {% endfor %} </table> {% endblock content %} This actually works but I do not know how to get the dates to show. Obviously {{ created }} doesn't do anything but the servers don't have create dates. Backups do and because it's a cron job there should only be X number of rows with any particular date (depending on how many servers we are following for that day). Summary I want to create a table, X being server names, Y being dates starting at today while all the cells being the status of a backup. The above model and template should hopefully give you an idea what my thought process but I am willing to alter anything. Basically I am create a fancy excel spreadsheet.

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  • How do I find the top N batters per year?

    - by Drew Stephens
    I'm playing around with the Lahman Baseball Database in a MySQL instance. I want to find the players who topped home runs (HR) for each year. The Batting table has the following (relevant parts) of its schema: +-----------+----------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+----------------------+------+-----+---------+-------+ | playerID | varchar(9) | NO | PRI | | | | yearID | smallint(4) unsigned | NO | PRI | 0 | | | HR | smallint(3) unsigned | YES | | NULL | | +-----------+----------------------+------+-----+---------+-------+ For each year, every player has an entry (between hundreds and 12k per year, going back to 1871). Getting the top N hitters for a single year is easy: SELECT playerID,yearID,HR FROM Batting WHERE yearID=2009 ORDER BY HR DESC LIMIT 3; +-----------+--------+------+ | playerID | yearID | HR | +-----------+--------+------+ | pujolal01 | 2009 | 47 | | fieldpr01 | 2009 | 46 | | howarry01 | 2009 | 45 | +-----------+--------+------+ But I'm interested in finding the top 3 from every year. I've found solutions like this, describing how to select the top from a category and I've tried to apply it to my problem, only to end up with a query that never returns: SELECT b.yearID, b.playerID, b.HR FROM Batting AS b LEFT JOIN Batting b2 ON (b.yearID=b2.yearID AND b.HR <= b2.HR) GROUP BY b.yearID HAVING COUNT(*) <= 3; Where have I gone wrong?

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  • How can i return dataset perfectly from sql?

    - by Phsika
    i try to write a winform application: i dislike below codes: DataTable dt = new DataTable(); dt.Load(dr); ds = new DataSet(); ds.Tables.Add(dt); Above part of codes looks unsufficient.How can i best loading dataset? public class LoadDataset { public DataSet GetAllData(string sp) { return LoadSQL(sp); } private DataSet LoadSQL(string sp) { SqlConnection con = new SqlConnection(ConfigurationSettings.AppSettings["ConnectionString"].ToString()); SqlCommand cmd = new SqlCommand(sp, con); DataSet ds; try { con.Open(); cmd.CommandType = CommandType.StoredProcedure; SqlDataReader dr = cmd.ExecuteReader(); DataTable dt = new DataTable(); dt.Load(dr); ds = new DataSet(); ds.Tables.Add(dt); return ds; } finally { con.Dispose(); cmd.Dispose(); } } }

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  • Should I catch exceptions thrown when closing java.sql.Connection

    - by jb
    Connection.close() may throw SqlException, but I have always assumed that it is safe to ignore any such exceptions (and I have never seen code that does not ignore them). Normally I would write: try{ connection.close(); }catch(Exception e) {} Or try{ connection.close(); }catch(Exception e) { logger.log(e.getMessage(), e); } The question is: Is it bad practice (and has anyone had problems when ignoring such exeptions). When Connection.close() does throw any exception. If it is bad how should I handle the exception. Comment: I know that discarding exceptions is evil, but I'm reffering only to exceptions thrown when closing a connection (and as I've seen this is fairly common in this case). Does anyone know when Connection.close() may throw anything?

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  • What's wrong with this SQL query?

    - by ThinkingInBits
    I have two tables: photographs, and photograph_tags. Photograph_tags contains a column called photograph_id (id in photographs). You can have many tags for one photograph. I have a photograph row related to three tags: boy, stream, and water. However, running the following query returns 0 rows SELECT p.* FROM photographs p, photograph_tags c WHERE c.photograph_id = p.id AND (c.value IN ('dog', 'water', 'stream')) GROUP BY p.id HAVING COUNT( p.id )=3 Is something wrong with this query?

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  • LINQtoSQL: Query to return List<String>

    - by ctrlShiftBryan
    I have a LINQ query that returns some object like this... var query = from c in db.Customers where ... select c; Then I do this List<String> list = new List<String>(); foreach (ProgramLanguage c in query) { //GetUL returns a String list.Add(GetUL(c.Property,c.Property2)); } Is there a way to combine into something list this? var query = from c in db.Customers where ... select new { GetUL(c.Property,c.Property2) }).ToList<String>();

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  • ASP.Net Gridview paging, pageindex always == 0.

    - by David Archer
    Hi all, Having a slight problem with my ASP.Net 3.5 app. I'm trying to get the program to pick up what page number has been clicked. I'm using ASP.Net's built in AllowPaging="True" function. It's never the same without code, so here it is: ASP.Net: <asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333" GridLines="Vertical" Width="960px" AllowSorting="True" EnableSortingAndPagingCallbacks="True" AllowPaging="True" PageSize="25" > <RowStyle BackColor="#F7F6F3" ForeColor="#333333" /> <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" /> <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" /> <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" /> <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" /> <EditRowStyle BackColor="#999999" /> <AlternatingRowStyle BackColor="White" ForeColor="#284775" /> </asp:GridView> C#: var fillTable = from ft in db.IncidentDatas where ft.pUserID == Convert.ToInt32(ClientList.SelectedValue.ToString()) select new { Reference = ft.pRef.ToString(), Date = ft.pIncidentDateTime.Value.Date.ToShortDateString(), Time = ft.pIncidentDateTime.Value.TimeOfDay, Premesis = ft.pPremises.ToString(), Latitude = ft.pLat.ToString(), Longitude = ft.pLong.ToString() }; if (fillTable.Count() > 0) { GridView1.DataSource = fillTable; GridView1.DataBind(); var IncidentDetails = fillTable.ToList(); for (int i = 0; i < IncidentDetails.Count(); i++) { int pageno = GridView1.PageIndex; int pagenostart = pageno * 25; if (i >= pagenostart && i < (pagenostart + 25)) { //Processing } } } Any idea why GridView1.PageIndex is always = 0? The thing is, the processing works correctly for the grid view.... it will always go to the correct paging page, but it's always 0 when I try to get the number. Help!

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  • How can I get the rank of rows relative to total number of rows based on a field?

    - by Arms
    I have a scores table that has two fields: user_id score I'm fetching specific rows that match a list of user_id's. How can I determine a rank for each row relative to the total number of rows, based on score? The rows in the result set are not necessarily sequential (the scores will vary widely from one row to the next). I'm not sure if this matters, but user_id is a unique field. Edit @Greelmo I'm already ordering the rows. If I fetch 15 rows, I don't want the rank to be 1-15. I need it to be the position of that row compared against the entire table by the score property. So if I have 200 rows, one row's rank may be 3 and another may be 179 (these are arbitrary #'s for example only). Edit 2 I'm having some luck with this query, but I actually want to avoid ties SELECT s.score , s.created_at , u.name , u.location , u.icon_id , u.photo , (SELECT COUNT(*) + 1 FROM scores WHERE score > s.score) AS rank FROM scores s LEFT JOIN users u ON u.uID = s.user_id ORDER BY s.score DESC , s.created_at DESC LIMIT 15 If two or more rows have the same score, I want the latest one (or earliest - I don't care) to be ranked higher. I tried modifying the subquery with AND id > s.id but that ended up giving me an unexpected result set and different ties.

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  • Oracle SQL CMD Line!!!

    - by DAVID
    Hi when ever perform select statements in the command line tool it doesnt use all of the space.. ive modified buffer size and window size and it just doesnt work. here is the Screenshot http://img19.imageshack.us/img19/8954/cmdoracle.jpg

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  • Find the highest number of occurences in a column in SQL

    - by Ronnie
    Given this table: Order custName description to_char(price) A desa $14 B desb $14 C desc $21 D desd $65 E dese $21 F desf $78 G desg $14 H desh $21 I am trying to display the whole row where prices have the highest occurances, in this case $14 and $21 I believe there needs to be a subquery. So i started out with this: select max(count(price)) from orders group by price which gives me 3. after some time i didn't think that was helpful. i believe i needed the value 14 and 21 rather the the count so i can put that in the where clause. but I'm stuck how to display that. any help?

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  • Postgresql Altering Table

    - by Jahn
    Is it possible to alter a table to add a new column and make that column a foreign key to another table in a single command in Postgresql? "alter table x add column y id references z(id)" doesn't seem to work as I had hoped.

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  • Put logic behind generated LinqToSql fields

    - by boris callens
    In a database I use throughout several projects, there is a field that should actually be a boolean but is for reasons nobody can explain to me a field duplicated over two tables where one time it is a char ('Y'/'N') and one time an int (1/0). When I generate a datacontext with LinqToSql the fields off course gets these datatypes. It would be nice if I don't have to drag this stupid choice of datatype throughout the rest of my application. Is there a way to give the generated classes a little bit of logic that just return me return this.equals('Y'); and return this==1; Preferably without having to make an EXTRA field in my partial class. It would be a solution to give the generated field a totally different name that can only be accessed through the partial class and then generate the extra field with the original name with my custom logic in the partial class. I don't know how to alter the accesibility level in my generated class though.. Any suggestions?

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  • Varchar columns: Nullable or not.

    - by NYSystemsAnalyst
    The database development standards in our organization state the varchar fields should not allow null values. They should have a default value of an empty string (""). I know this makes querying and concatenation easier, but today, one of my coworkers questioned me about why that standard only existed for varchar types an not other datatypes (int, datetime, etc). I would like to know if others consider this to be a valid, defensible standard, or if varchar should be treated the same as fields of other data types? I believe this standard is valid for the following reason: I believe that an empty string and null values, though technically different, are conceptually the same. An empty, zero length string is a string that does not exist. It has no value. However, a numeric value of 0 is not the same as NULL. For example, if a field called OutstandingBalance has a value of 0, it means there are $0.00 remaining. However, if the same field is NULL, that means the value is unknown. On the other hand, a field called CustomerName with a value of "" is basically the same as a value of NULL because both represent the non-existence of the name. I read somewhere that an analogy for an empty string vs. NULL is that of a blank CD vs. no CD. However, I believe this to be a false analogy because a blank CD still phyically exists and still has physical data space that does not have any meaningful data written to it. Basically, I believe a blank CD is the equivalent of a string of blank spaces (" "), not an empty string. Therefore, I believe a string of blank spaces to be an actual value separate from NULL, but an empty string to be the absense of value conceptually equivalent to NULL. Please let me know if my beliefs regarding variable length strings are valid, or please enlighten me if they are not. I have read several blogs / arguments regarding this subject, but still do not see a true conceptual difference between NULLs and empty strings.

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