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  • Representing Sparse Data in PostgreSQL

    - by Chris S
    What's the best way to represent a sparse data matrix in PostgreSQL? The two obvious methods I see are: Store data in a single a table with a separate column for every conceivable feature (potentially millions), but with a default value of NULL for unused features. This is conceptually very simple, but I know that with most RDMS implementations, that this is typically very inefficient, since the NULL values ususually takes up some space. However, I read an article (can't find its link unfortunately) that claimed PG doesn't take up data for NULL values, making it better suited for storing sparse data. Create separate "row" and "column" tables, as well as an intermediate table to link them and store the value for the column at that row. I believe this is the more traditional RDMS solution, but there's more complexity and overhead associated with it. I also found PostgreDynamic, which claims to better support sparse data, but I don't want to switch my entire database server to a PG fork just for this feature. Are there any other solutions? Which one should I use?

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  • Using outer query result in a subquery in postgresql

    - by brad
    I have two tables points and contacts and I'm trying to get the average points.score per contact grouped on a monthly basis. Note that points and contacts aren't related, I just want the sum of points created in a month divided by the number of contacts that existed in that month. So, I need to sum points grouped by the created_at month, and I need to take the count of contacts FOR THAT MONTH ONLY. It's that last part that's tricking me up. I'm not sure how I can use a column from an outer query in the subquery. I tried something like this: SELECT SUM(score) AS points_sum, EXTRACT(month FROM created_at) AS month, date_trunc('MONTH', created_at) + INTERVAL '1 month' AS next_month, (SELECT COUNT(id) FROM contacts WHERE contacts.created_at <= next_month) as contact_count FROM points GROUP BY month, next_month ORDER BY month So, I'm extracting the actual month that my points are being summed, and at the same time, getting the beginning of the next_month so that I can say "Get me the count of contacts where their created at is < next_month" But it complains that column next_month doesn't exist This is understandable as the subquery knows nothing about the outer query. Qualifying with points.next_month doesn't work either. So can someone point me in the right direction of how to achieve this? Tables: Points score | created_at 10 | "2011-11-15 21:44:00.363423" 11 | "2011-10-15 21:44:00.69667" 12 | "2011-09-15 21:44:00.773289" 13 | "2011-08-15 21:44:00.848838" 14 | "2011-07-15 21:44:00.924152" Contacts id | created_at 6 | "2011-07-15 21:43:17.534777" 5 | "2011-08-15 21:43:17.520828" 4 | "2011-09-15 21:43:17.506452" 3 | "2011-10-15 21:43:17.491848" 1 | "2011-11-15 21:42:54.759225" sum, month and next_month (without the subselect) sum | month | next_month 14 | 7 | "2011-08-01 00:00:00" 13 | 8 | "2011-09-01 00:00:00" 12 | 9 | "2011-10-01 00:00:00" 11 | 10 | "2011-11-01 00:00:00" 10 | 11 | "2011-12-01 00:00:00"

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  • how to 'scale' these three tables?

    - by iddqd
    I have the following Tables: Players id playerName Weapons id type otherData Weapons2Player id playersID_reference weaponsID_reference That was nice and simple. Now I need to SELECT items from the Weapons table, according to some of their characteristics that i previously just packed into the otherData column (since it was only needed on the client side). The problem is, that the types have varying characteristics - but also a lot of similar data. So I'm trying to decide on the following possibilities, all of which have their pros and cons. Solution A Kill the Weapons table, and create a new table for each Weapon-Type: Weapons_Swords id bladeType damage otherData Weapons_Guns id accuracy damage ammoType otherData But how will i Link these to the Players ? create Weapons_Swords2Players, Weapons_Guns2Players for each weapon-type? (Will result in a lot more JOINS when loading the player with all his weapons...and it's also more complicated to insert a new player) or add another column to Weapons2Players called WeaponsTypeTable, then do sub-selects to the correct Weapons sub-table (seems easier, but not really right, slightly easier insert i guess) Solution B Keep the Weapons table, and add all the fields i need to it. The Problem is that then there will be NULL fields, since not all Weapon-Types use all fields (can't be right) Weapons id type accuracy damage ammoType bladeType otherData This seems to be pretty basic stuff, but i just can't decide what's best. Or is there a correct Solution C? many thanks.

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  • MySQL optimized sentence

    - by Ivan
    I have a simple table where I have to extract some records. The problem is that the evaluation function is a very time-consuming stored procedure so I shouldn't to call it twice like in this sentence: SELECT *, slow_sp(row) FROM table WHERE slow_sp(row)>0 ORDER BY dist DESC LIMIT 10 First I thought in optimize like this: SELECT *, slow_sp(row) AS value FROM table WHERE value>0 ORDER BY dist DESC LIMIT 10 But it doesn't works due "value" is not processed when the WHERE clause is evaluated. Any idea to optimize this sentence? Thanks.

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  • How to get the last element by date of each "type" in LINQ or TSQL

    - by Mauro
    Imagine to have a table defined as CREATE TABLE [dbo].[Price]( [ID] [int] NOT NULL, [StartDate] [datetime] NOT NULL, [Price] [int] NOT NULL ) where ID is the identifier of an action having a certain Price. This price can be updated if necessary by adding a new line with the same ID, different Price, and a more recent date. So with a set of a data like ID StartDate Price 1 01/01/2009 10 1 01/01/2010 20 2 01/01/2009 10 2 01/01/2010 20 How to obtain a set like the following? 1 01/01/2010 20 2 01/01/2010 20

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  • Help to choose NoSQL database for project

    - by potapuff
    There is a table: doc_id(integer)-value(integer) Approximate 100k doc_id and 27?? rows. Majority query on this table - searching documents similar to current document: select 10 documents with maximum of (count common to current document value)/(count ov values in document). Nowadays we use PostgreSQL. Table weight (with index) ~1,5 GB. Average query time ~0.5s. Should I transfer all this to NoSQL base, if so, what?

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  • SSRS report combine data sources and generate csv

    - by Nithin
    I am new to ssrs. I have a report that gets data from two databases. I can create two datasets that connect to two different databases. The databases are third party and I cannot create stored procedures on the databases. My issue is that I have to combine the data from the two queries. Please help me with this issue or point me to locations where I can find answers. Thanks in advance.

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  • Embedding generic sql queries into c# program

    - by Pooja Balkundi
    Okay referring to my first question code in the main, I want the user to enter employee name at runtime and then i take this name which user has entered and compare it with the e_name of my emp table , if it exists i want to display all information of that employee , how can I achieve this ? using System; using System.Collections.Generic; using System.Linq; using System.Windows.Forms; using MySql.Data.MySqlClient; namespace ConnectCsharppToMySQL { public class DBConnect { private MySqlConnection connection; private string server; private string database; private string uid; private string password; string name; //Constructor public DBConnect() { Initialize(); } //Initialize values private void Initialize() { server = "localhost"; database = "test"; uid = "root"; password = ""; string connectionString; connectionString = "SERVER=" + server + ";" + "DATABASE=" + database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";"; connection = new MySqlConnection(connectionString); } //open connection to database private bool OpenConnection() { try { connection.Open(); return true; } catch (MySqlException ex) { //When handling errors, you can your application's response based //on the error number. //The two most common error numbers when connecting are as follows: //0: Cannot connect to server. //1045: Invalid user name and/or password. switch (ex.Number) { case 0: MessageBox.Show("Cannot connect to server. Contact administrator"); break; case 1045: MessageBox.Show("Invalid username/password, please try again"); break; } return false; } } //Close connection private bool CloseConnection() { try { connection.Close(); return true; } catch (MySqlException ex) { MessageBox.Show(ex.Message); return false; } } //Insert statement public void Insert() { string query = "INSERT INTO emp (e_name, age) VALUES('Pooja R', '21')"; //open connection if (this.OpenConnection() == true) { //create command and assign the query and connection from the constructor MySqlCommand cmd = new MySqlCommand(query, connection); //Execute command cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Update statement public void Update() { string query = "UPDATE emp SET e_name='Peachy', age='22' WHERE e_name='Pooja R'"; //Open connection if (this.OpenConnection() == true) { //create mysql command MySqlCommand cmd = new MySqlCommand(); //Assign the query using CommandText cmd.CommandText = query; //Assign the connection using Connection cmd.Connection = connection; //Execute query cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Select statement public List<string>[] Select() { string query = "SELECT * FROM emp where e_name=(/*I WANT USER ENTERED NAME TO GET INSERTED HERE*/)"; //Create a list to store the result List<string>[] list = new List<string>[3]; list[0] = new List<string>(); list[1] = new List<string>(); list[2] = new List<string>(); //Open connection if (this.OpenConnection() == true) { //Create Command MySqlCommand cmd = new MySqlCommand(query, connection); //Create a data reader and Execute the command MySqlDataReader dataReader = cmd.ExecuteReader(); //Read the data and store them in the list while (dataReader.Read()) { list[0].Add(dataReader["e_id"] + ""); list[1].Add(dataReader["e_name"] + ""); list[2].Add(dataReader["age"] + ""); } //close Data Reader dataReader.Close(); //close Connection this.CloseConnection(); //return list to be displayed return list; } else { return list; } } public static void Main(String[] args) { DBConnect db1 = new DBConnect(); Console.WriteLine("Initializing"); db1.Initialize(); Console.WriteLine("Search :"); Console.WriteLine("Enter the employee name"); db1.name = Console.ReadLine(); db1.Select(); Console.ReadLine(); } } }

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  • Problem with interface implementation in partial classes.

    - by Bas
    I have a question regarding a problem with L2S, Autogenerated DataContext and the use of Partial Classes. I have abstracted my datacontext and for every table I use, I'm implementing a class with an interface. In the code below you can see I have the Interface and two partial classes. The first class is just there to make sure the class in the auto-generated datacontext inherets Interface. The other autogenerated class makes sure the method from Interface is implemented. namespace PartialProject.objects { public interface Interface { Interface Instance { get; } } //To make sure the autogenerated code inherits Interface public partial class Class : Interface { } //This is autogenerated public partial class Class { public Class Instance { get { return this.Instance; } } } } Now my problem is that the method implemented in the autogenerated class gives the following error: - Property 'Instance' cannot implement property from interface 'PartialProject.objects.Interface'. Type should be 'PartialProjects.objects.Interface'. <- Any idea how this error can be resolved? Keep in mind that I can't edit anything in the autogenerated code. Thanks in advance!

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  • SSMS Results to Grid - CRLF not preserved in copy/paste - any better techniques?

    - by Cade Roux
    When I have a result set in the grid like: SELECT 'line 1 line 2 line 3' or SELECT 'line 1' + CHAR(13) + CHAR(10) + 'line 2' + CHAR(13) + CHAR(10) + 'line 3' With embedded CRLF, the display in the grid appears to replace them with spaces (I guess so that they will display all the data). The problem is that if I am code-generating a script, I cannot simply cut and paste this. I have to convert the code to open a cursor and print the relevant columns so that I can copy and paste them from the text results. Is there any simpler workaround to preserve the CRLF in a copy/paste operation from the results grid? The reason that the grid is helpful is that I am currently generating a number of scripts for the same object in different columns - a bcp out in one column, an xml format file in another, a table create script in another, etc...

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  • Testing the context in asp.net mvc

    - by user252160
    I got pretty experienced with testing controllers, my question here is though, aren't we supposed to test the data context as well, and how ? I mean, there are a lot of relationships and constraints coming from the DB that simply testing controllers does not cover. On the other hand, testing against the DB is not considered a good practice - what then ? Simply testing without db.SubmitChanges() or what ?

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  • Count times ID appears in a table and return in row.

    - by Tyler
    SELECT Boats.id, Boats.date, Boats.section, Boats.raft, river_company.company, river_section.section AS river FROM Boats INNER JOIN river_company ON Boats.raft = river_company.id INNER JOIN river_section ON Boats.section = river_section.id ORDER BY Boats.date DESC, river, river_company.company Returns everything I need. But how would I add a [Photos] table and count how many times Boats.id occurs in it and add that to the returned rows. So if there are 5 photos for boat #17 I want the record for boat #17 to say PhotoCount = 5

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  • Sqlite View : Add a column based on some other column

    - by NightCoder
    Hi, I have two tables Employee ID | Name | Department ---------------------- 121 |Name1 | dep1 223 |Name2 | dep2 Assignment ID | EID| --------- 1 |121 2 |223 3 |121 [other columns omitted for brevity] The table assignment indicates which is work is assigned to whom.EID is a foriegn key to the table Employee.Also it is possible to have two work assigned to the same employee. Now i want to create a view like this EID | Assigned -------------- 121 |true 333 |false Assigned column should be calculated based on the entries in the Assignment table. So far i am only successful in creating a view like this EID | Assigned -------------- 121 |2 333 |0 using the command CREATE VIEW "AssignmentView" AS SELECT distinct ID ,(select Count(*) from Assignment where Assignment.EID = Employee.ID) as Assigned FROM Employee; Thanks

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  • What are the benefits of left outer join vs nested aggregate selects to find the newest rows in a table?

    - by RenderIn
    I'm doing: select * from mytable y where y.year = (select max(yi.year) from mytable yi where yi.person = y.person) Is that better or worse from a performance aspect than: select y.* from mytable y left outer join mytable y2 on y.year < y2.year and y.person = y2.person where y2.year is null The explain plan/anecdotal evidence is inconclusive so I am wondering if in general one is better than the other.

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  • How to get query result even if JOIN hasn't found any results?

    - by user1734651
    I want select data for user, and join another info from other table that related to the user. The problem is that this extra data not always exist for any user, just for few. How can I write a query that will return NULL for not found data, instead just return null for the whole query? SELECT a.*, b.* FROM user AS a LEFT JOIN extra AS b ON (a.userid = b.userid) WHERE a.userid = {$userid} LIMIT 1 When extra data found for the user, I get the resource as expected. If not, I get NULL for the whole query. Bottom line, I don't care if "extra" exist for the user or not, if yes - select it as well, if not - ignore that.

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  • Connect sortable lists together and update SQL using jQuery UI

    - by rebellion
    I'm using jQuery UI's sortable lists to sort items in a todo list, and the reordering of the lists works like a charm. I have several UL lists for each todo category, i.e. Design, Development, etc. I want to be able to move an item from one category to another, and jQuery UI's sortable lists plugin allows me to do this with the connectWith option parameter. But I can't seem to find how to update the database as well. The todo database table has a field for a reference to the category which is laying in it's own table. This is the current code: $('.sortable').sortable({ axis: 'y', opacity: .5, cancel: '.no-tasks', connectWith: '.sortable', update: function(){ $.ajax({ type: 'POST', url: basepath + 'task/sort_list', data: $(this).sortable('serialize') }); } }); Do I need to add another value to the AJAX's data parameter, or do the sortable plugin this for me in the serialize function?

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  • ROW_NUMBER() VS. DISTINCT

    - by ramadan2050
    Dear All, I have a problem with ROW_NUMBER() , if i used it with DISTINCT in the following Query I have 2 scenarios: 1- run this query direct : give me for example 400 record as a result 2- uncomment a line which start with [--Uncomment1--] : give me 700 record as a result it duplicated some records not all the records what I want is to solve this problem or to find any way to show a row counter beside each row, to make a [where rownumber between 1 and 30] --Uncomment2-- if I put the whole query in a table, and then filter it , it is work but it still so slow waiting for any feedback and I will appreciate that Thanks in advance SELECT * FROM (SELECT Distinct CRSTask.ID AS TaskID, CRSTask.WFLTaskID, --Uncomment1-- ROW_NUMBER() OVER (ORDER By CRSTask.CreateDate asc ) AS RowNum , CRSTask.WFLStatus AS Task_WFLStatus, CRSTask.Name AS StepName, CRSTask.ModifiedDate AS Task_ModifyDate, CRSTask.SendingDate AS Task_SendingDate, CRSTask.ReceiveDate AS Task_ReceiveDate, CRSTask.CreateDate AS Task_CreateDate, CRS_Task_Recipient_Vw.Task_CurrentSenderName, CRS_Task_Recipient_Vw.Task_SenderName, CRS_INFO.ID AS CRS_ID, CRS_INFO.ReferenceNumber, CRS_INFO.CRSBeneficiaries, CRS_INFO.BarCodeNumber, ISNULL(dbo.CRS_FNC_GetTaskReceiver(CRSTask.ID), '') + ' ' + ISNULL (CRS_Organization.ArName, '') AS OrgName, CRS_Info.IncidentID, COALESCE(CRS_Subject.ArSubject, '??? ????') AS ArSubject, COALESCE(CRS_INFO.Subject, 'Blank Subject') AS CRS_Subject, CRS_INFO.Mode, CRS_Task_Recipient_Vw.ReceiverID, CRS_Task_Recipient_Vw.ReceiverType, CRS_Task_Recipient_Vw.CC, Temp_Portal_Users_View.ID AS CRS_LockedByID, Temp_Portal_Users_View.ArabicName AS CRS_LockedByName, CRSDraft.ID AS DraftID, CRSDraft.Type AS DraftType, CASE WHEN CRS_Folder = 1 THEN Task_SenderName WHEN CRS_Folder = 2 THEN Task_SenderName WHEN CRS_Folder = 3 THEN Task_CurrentSenderName END AS SenderName, CRS_Task_Folder_Vw.CRS_Folder, CRS_INFO.Status, CRS_INFO.CRS_Type, CRS_Type.arName AS CRS_Type_Name FROM CRS_Task_Folder_Vw LEFT OUTER JOIN CRSTask ON CRSTask.ID = CRS_Task_Folder_Vw.TaskID LEFT OUTER JOIN CRS_INFO ON CRS_INFO.ID = CRSTask.CRSID LEFT OUTER JOIN CRS_Subject ON COALESCE( SUBSTRING( CRS_INFO.Subject, CHARINDEX('_', CRS_INFO.Subject) + 1, LEN(CRS_INFO.Subject) ), 'Blank Subject' ) = CRS_Subject.ID LEFT OUTER JOIN CRSInfoAttribute ON CRS_INFO.ID = CRSInfoAttribute.ID LEFT OUTER JOIN CRS_Organization ON CRS_Organization.ID = CRSInfoAttribute.SourceID LEFT OUTER JOIN CRS_Type ON CRS_INFO.CRS_Type = CRS_Type.ID LEFT OUTER JOIN CRS_Way ON CRS_INFO.CRS_Send_Way = CRS_Way.ID LEFT OUTER JOIN CRS_Priority ON CRS_INFO.CRS_Priority_ID = CRS_Priority.ID LEFT OUTER JOIN CRS_SecurityLevel ON CRS_INFO.SecurityLevelID = CRS_SecurityLevel.ID LEFT OUTER JOIN Portal_Users_View ON Portal_Users_View.ID = CRS_INFO.CRS_Initiator LEFT OUTER JOIN AD_DOC_TBL ON CRS_INFO.DocumentID = AD_DOC_TBL.ID LEFT OUTER JOIN CRSTask AS Temp_CRSTask ON CRSTask.ParentTask = Temp_CRSTask.ID LEFT OUTER JOIN Portal_Users_View AS Temp_Portal_Users_View ON Temp_Portal_Users_View.ID = AD_DOC_TBL.Lock_User_ID LEFT OUTER JOIN Portal_Users_View AS Temp1_Portal_Users_View ON Temp1_Portal_Users_View.ID = CRS_INFO.ClosedBy LEFT OUTER JOIN CRSDraft ON CRSTask.ID = CRSDraft.TaskID LEFT OUTER JOIN CRS_Task_Recipient_Vw ON CRSTask.ID = CRS_Task_Recipient_Vw.TaskID --LEFT OUTER JOIN CRSTaskReceiverUsers ON CRSTask.ID = CRSTaskReceiverUsers.CRSTaskID AND CRS_Task_Recipient_Vw.ReceiverID = CRSTaskReceiverUsers.ReceiverID LEFT OUTER JOIN CRSTaskReceiverUserProfile ON CRSTask.ID = CRSTaskReceiverUserProfile.TaskID WHERE Crs_Info.SUBJECT <> 'Blank Subject' AND (CRS_INFO.Subject NOT LIKE '%null%') AND CRS_Info.IsDeleted <> 1 /* AND CRSTask.WFLStatus <> 6 AND CRSTask.WFLStatus <> 8 */ AND ( ( CRS_Task_Recipient_Vw.ReceiverID IN (1, 29) AND CRS_Task_Recipient_Vw.ReceiverType IN (1, 3, 4) ) ) AND 1 = 1 )Codes --Uncomment2-- WHERE Codes.RowNum BETWEEN 1 AND 30 ORDER BY Codes.Task_CreateDate ASC

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  • Why would I get a duplicate key error when updating a row?

    - by hdx
    I'm using postgres and I'm getting the duplicate key error when updating a row: cursor.execute("UPDATE jiveuser SET userenabled = 0 WHERE userid = %s" % str(userId)) psycopg2.IntegrityError: duplicate key value violates unique constraint "jiveuser_pk" I don't understand how updating a row can cause this error... any help will be much appreciated.

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  • filtering for multiple values on one column. All values must exist, else - return zero

    - by Andrew
    Hello All, I would like to filter one column in a table for couple values and show results only if all those values are there. If one or more is missing, then return zero results. example table +----+--------+----------+ | id | Fruit | Color | +----+--------+----------+ | 1 | apple | red | | 2 | mango | yellow | | 3 | banana | yellow | +----+--------+----------+ example "wrong" code: (this must return 3 rows) select Fruit FROM table WHERE Color = red AND Color = yellow but select Fruit FROM table WHERE Color = red AND Color = green must return 0 rows. (If i use select Fruit FROM table WHERE Color = red OR Color = green i get 1 row which is not what i need) I am using PHP with form where user checks different checkboxes that represent different values of the same column. So when he selects multiple checkboxes, all those values should be in the result set, otherwise no result should be given. Thank you, Andrew

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  • Restoring database with SMO - Reporting progress problems

    - by madlan
    I'm using the below to restore a database in VB.NET. This works but causes the interface to lockup if the user clicks anything. Also, I cannot get the progress label to update incrementally, it's blank until the backup is complete then displays 100% Sub DoRestore() Dim svr As Server = New Server("Server\SQL2008") Dim res As Restore = New Restore() res.Devices.AddDevice("C:\MyDB.bak", DeviceType.File) res.Database = "MyDB" res.RelocateFiles.Add(New RelocateFile("MyDB_Data", "C:\MyDB.mdf")) res.RelocateFiles.Add(New RelocateFile("MyDB_Log", "C:\MyDB.ldf")) res.PercentCompleteNotification = 1 AddHandler res.PercentComplete, AddressOf ProgressEventHandler res.SqlRestore(svr) End Sub Private Sub ProgressEventHandler(ByVal sender As Object, ByVal e As PercentCompleteEventArgs) Label3.Text = "" ProgressBar.Value = e.Percent LblProgress.Text = e.Percent.ToString End Sub

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  • Is there a special character in mySql that would return always true in WHERE clauses?

    - by rm.
    Is there a character, say, $, SELECT * FROM Persons WHERE firstName='Peter' AND areaCode=$; such that the statement would return the same as SELECT * FROM Persons WHERE firstName='Peter' i.e. areaCode=$ would always return always true and, thus, effectively “turns of” the criteria areaCode=... I’m writing a VBA code in Excel that fetches some rows based on a number of criteria. The criteria can either be enabled or disabled. A character like $ would make the disabling so much easier.

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  • Get sum of two columns in one LINQ query

    - by Axarydax
    Hi, let's say that I have a table called Items (ID int, Done int, Total int) I can do it by two queries: int total = m.Items.Sum(p=>p.Total) int done = m.Items.Sum(p=>p.Done) But I'd like to do it in one query, something like this: var x = from p in m.Items select new { Sum(p.Total), Sum(p.Done)}; Surely there is a way to call aggregate functions from LINQ syntax...?

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