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  • How to set up two models having a has_many association with each other

    - by daz13
    I'm looking for a suggestion on how to set up two models, Teacher and Subject. A Teacher can have many Subjects, and a Subject can have many Teachers. Another thing to consider in the relationship between the two models is that a Teacher can create a Subject and add other Teachers to the Subject. I think I'm solid on the basics of the set up for each model: for teacher.rb: has_many :subjects for subject.rb: has_many :teachers and the teachers table should have a subject_id column and the subject table should have a teacher_id column. What I'm not sure about is how to set up the views (and corresponding controller methods) to allow the addition of a Teacher to a Subject. Any suggestions (or links to examples) are greatly appreciated. I haven't been able to find anything on this exact case.

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  • How to convet DataTable to List on runtype with out existin class property [closed]

    - by shamim
    Work on VS2010 C#,Have one DataTable ,want to convert this DataTable to List Suppose: Table dt; On run time want to create similar field from a datatable and fill fields in List.There is no existing class for list properties. ListName=TableName List property name=Table column name List Property type=Table column type List items=Table rows Note: Recently work on EF.To fullfill my project requirement, need to give flexibility to use to input and execute ESQL at runtime .I don’t want to put this execute result on datatable or List ,want to put this result on list. List has no existing class and property,don’t want to convert DataTable on list Type:DataRow If have any query please ask,Thanks in advanced.

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  • comparing rows on a mysql table

    - by user311324
    Ok here's the deal I got one table with a bunch of client information. Each client makes up to one purchase a year which is represented by an individual row. there's a column for the year and there's a column the contains a unique identifier for each client. What I need to do is to construct a query that takes last year and this year and shows me which clients were here made a purchase last year but not make a purchase this year. I also need to build a query that shows me which clients did not make a purchase last year and the year before last but did make a purchase this year.

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  • UUID Cassandra.

    - by Sandeep
    Hi all, I am new to Cassandra. I am trying to insert some values to the columnfamily. The definition of columnfamily in the config file is as follows. <ColumnFamily Name="CommandQueue" ColumnType="Super" CompareWith="TimeUUIDType" CompareSubcolumnsWith="UTF8Type"/> When ever I try to insert values to I always get "InvalidRequestException(why: UUIDs must be exactly 16 bytes)". I am using batch_mutate() to insert column. How can I insert values to the column family.

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  • Entity Framework 4 and 0:1, 0:1 relationships

    - by Eric J.
    I'm using the Model First approach with EF 4 and hit a snag with two tables, Participant (singular because pre-existing from another app) and ActiveParticipants. A Participant may or may not be associated with exactly one ActiveParticipant and vice versa. When I create an association, everything seems to go well on the surface, but then I get a runtime error complaining that Participant does not contain the column ActiveParticipant_Id. It does contain a column ActiveParticipantId (no underscore). When I view the diagram as XML, there's a line like this: <Property Name="ActiveParticipant_Id" Type="uniqueidentifier" Nullable="true" /> Why is it adding an underscore? Is there anything special I need to do for 0:1, 0:1 relationships?

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  • Combining IN and NOT IN in SQL as single result

    - by UltraVi01
    I apologize for the vague title. I am attempting to write a query that returns an alias column with matching values (resulting from an IN) as well as an alias column with values that do not match (using NOT IN). I want the result set to have: userId | matches | nonmatches. I currently have the following query which returns the matches as expected. I am having trouble getting the nonmatches in the result set -- that is, from a NOT IN statement SET @userId = 9; SELECT ug.user_id, COUNT(DISTINCT goal_id) as matches FROM user_goal ug WHERE ug.user_id!=@userId AND goal_id IN (SELECT iug.goal_id FROM user_goal iug WHERE user_id=@userId) GROUP BY user_id ORDER BY matches DESC LIMIT 4 So, the NOT IN would look something like this: goal_id NOT IN(SELECT uggg.goal_id FROM user_goal uggg WHERE user_id=@userId) AS nonmatches I am just not sure how to incorporate the NOT IN statement in my query so I get all the results

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  • Determining child count of path

    - by sqlnewbie
    I have a table whose 'path' column has values and I would like to update the table's 'child_count' column so that I get the following output. path | child_count --------+------------- | 5 /a | 3 /a/a | 0 /a/b | 1 /a/b/c | 0 /b | 0 My present solution - which is way too inefficient - uses a stored procedure as follows: CREATE FUNCTION child_count() RETURNS VOID AS $$ DECLARE parent VARCHAR; BEGIN FOR parent IN SELECT path FROM my_table LOOP DECLARE tokens VARCHAR[] := REGEXP_SPLIT_TO_ARRAY(parent, '/'); str VARCHAR := ''; BEGIN FOR i IN 2..ARRAY_LENGTH(tokens, 1) LOOP UPDATE my_table SET child_count = child_count + 1 WHERE path = str; str := str || '/' || tokens[i]; END LOOP; END; END LOOP; END; $$ LANGUAGE plpgsql; Anyone knows of a single UPDATE statement that does the same thing?

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  • How to Merge two databases in one in MS SQL Server 2008?

    - by SzamDev
    Hi I have 2 PCs, each one of them has MS SQL Server 2008 installed on it and there is a database with data in it. I need a way that I can move data in my DB from this MS SQL Server to another one (another PC which has the same DB) move data from one PC to another one - There is one proplem, the ID column, because each DB in my 2 PCs has data in it so this column counts from 1,2,3,....... ( data will be conflict with other data in my DB ) Is there any way to solve my proplem and move data successfully?

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  • SQL: Optimize insensive SELECTs on DateTime fields

    - by Fedyashev Nikita
    I have an application for scheduling certain events. And all these events must be reviewed after each scheduled time. So basically we have 3 tables: items(id, name) scheduled_items(id, item_id, execute_at - datetime) - item_id column has an index option. reviewed_items(id, item_id, created_at - datetime) - item_id column has an index option. So core function of the application is "give me any items(which are not yet reviewed) for the actual moment". How can I optimize this solution for speed(because it is very core business feature and not micro optimization)? I suppose that adding index to the datetime fields doesn't make any sense because the cardinality or uniqueness on that fields are very high and index won't give any(?) speed-up. Is it correct? What would you recommend? Should I try no-SQL? -- mysql -V 5.075 I use caching where it makes sence.

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  • How to read and loop through each rows in an Excel using C#

    - by Ullan
    I need to read an excel file and loop through the rows. I used the below code to read the excel file. But I am not getting the entire row, inseatd of getting the column values. try { OleDbConnection objConnection = new OleDbConnection(strConnectionString); string queryString = string.Format("Select * from [{0}$]", strSheetName, objConnection); OleDbCommand command = new OleDbCommand(queryString, objConnection); objConnection.Open(); OleDbDataReader reader = command.ExecuteReader(); while (reader.Read()) { var val1 = reader[0].ToString(); //Here I want to get each row } reader.Close(); } catch (Exception ex) { Console.WriteLine(ex.Message); } I need to check if the row is empty or not, if not empty, I need to serach for some values in a particular column. Thanks for your help

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  • How can I get a set of radio buttons to accept NULL (nothing checked)?

    - by Ethan
    I'm working on a Rails application where I have some a set of two radio buttons where users can click "yes" or "no". The MySQL DB column created by the ActiveRecord migration is a tinyint. If the user doesn't click either radio button I want MySQL to store NULL. (The column allows NULL.) And when they come back to edit the data, neither button should be checked. What's happening is that ActiveRecord is storing 0 and then when I come back the "No" button is checked. Rails 2.3.5 Form code (I'm using Haml): = f.radio_button( :model_attribute, true ) Yes = f.radio_button( :model_attribute, false ) No (In retrospect it probably would have been better to use a single checkbox, but it would be difficult to change that now.)

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  • C#: Select row from DataGridView

    - by Bi
    Hi I have a form with a DataGridView (of 3 columns) and a Button. Every time the user clicks on a button, I want the get the values stored in the 1st column of that row. Here is the code I have: private void myButton_Click(object sender, EventArgs e) { foreach (DataGridViewRow row in ProductsGrid.Rows) { if (this.ProductsGrid.SelectedRows.Count == 1) { // get information of 1st column from the row string value = this.ProductsGrid.SelectedRows[0].Cells[0].ToString(); } } } However when I click on myButton, the this.ProductsGrid.SelectedRows.Count is 0. Also, how do I ensure that the user selects only one row and not multiple rows? Does this code look right?

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  • Can MySQL automatically specify `_utf8` for inserts to UTF-8 columns?

    - by Neil
    I have a table like this, where one column is latin1, the other is UTF-8: Create Table: CREATE TABLE `names` ( `name_english` varchar(255) character NOT NULL, `name_chinese` varchar(255) character set utf8 default NULL, ) ENGINE=MyISAM DEFAULT CHARSET=latin1 When I do an insert, I have to type _utf8 before values being inserted into UTF-8 columns: insert into names (name_english = "hooey", name_chinese = _utf8 "??"); However, since MySQL should know that name_chinese is a UTF-8 column, it should be able to know to use _utf8 automatically. Is there any way to tell MySQL to use _utf8 automatically, so when I'm programatically making prepared statements, I don't have to worry about including it with the right parameters?

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  • TDBGrid columns design time or run time?

    - by Mawg
    I am using TDBGrid for the first time. I didn't even notice the Columns property in the object inspector and everything went just fine: the grid was filled. Then I saw the Columns property and tried it. When I use the object insector to add items to the Columns property of the grid, they do not all of them show up at run time. To me, it looks like the FieldName property is important. It looks like it is correct, but there are no values in some columns. If I leave this property blank (no columns at all) it seems that the control populates it itself at run time and I do see all the columns. I could live with that. When I set column titles at run time it works, but setting column width does not.

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  • How do I transform a single colmn list to item matrix in R?

    - by Indy
    I currently have data that is in the following format (note, this is 1 column, 4 row matrix): aa|bb bb|cc|ee|ee cc cc|ee and I want it displayed so that the column names are: aa, bb, cc, dd, and ee. And I want there to be 4 row such that each row counts the number of times each string was present in the matching row above. ie) aa bb cc dd ee 1 1 0 0 0 0 1 1 0 2 0 0 1 0 0 0 0 1 0 1 Does anyone know how to do this in R? I would post my attempt, but it is just getting ugly and complicated. Any help would be much appreciated. Thanks in advance.

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  • Displaying a well formatted table

    - by user1378680
    Please take a look at the picture below. The header for the second column is displaying DISTRICT under SENATORIAL. But that's not the case for the 2nd and 3rd Rows under the 2nd Column. What I want to achieve is that words/strings should not ba able to extend width of the table.... The CSS I'm using is beneath. table { width: 650px; font-family: calibri; word-wrap: break-word; margin-left: 115px; } th { padding: 3px; color: white; text-transform: uppercase; font-size: 12px; background-image: url(navbg.png); font-weight: normal; word-wrap: break-word; font-family: "Trebuchet MS"; } Image:

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  • Why is [date] + [time] non-deterministic in SQL Server 2008?

    - by John Gietzen
    I'm trying to do the following for my IIS logs table: ALTER TABLE [W3CLog] ADD [LogTime] AS [date] + ([time] - '1900-01-01') PERSISTED However, SQL Server 2008 tells me: Computed column 'LogTime' in table 'W3CLog' cannot be persisted because the column is non-deterministic. The table has this definition: CREATE TABLE [dbo].[W3CLog]( [Id] [bigint] IDENTITY(1,1) NOT NULL, ... [date] [datetime] NULL, [time] [datetime] NULL, ... ) Why is that non-deterministic? I really need to index that field. The table currently has 1598170 rows, and it is a pain to query if we can't do an index seek on the full time. Since this is being UNION'd with some other log formats, we can't very easily just use the two columns separately.

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  • SQL - logical AND among multiple rows

    - by potrnd
    Hello, First of all sorry that I could not think of a more descriptive title. What I want to do is the following using only SQL: I have some lists of strings, list1, list2 and list3. I have a dataset that contains two interesting columns, A and B. Column A contains a TransactionID and column B contains an ItemID. Naturally, there can be multiple rows that share the same TransactionIDs. I need to catch those transactions that have at least one item ID that exists whithin each list (list1, list2 AND list3). I also need to count how many times does that happen for each transaction. I hope that makes enough sense, perhaps I will be able to explain it better with a clear head. Thanks in advance

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  • Improve C function performance with cache locality?

    - by Christoper Hans
    I have to find a diagonal difference in a matrix represented as 2d array and the function prototype is int diagonal_diff(int x[512][512]) I have to use a 2d array, and the data is 512x512. This is tested on a SPARC machine: my current timing is 6ms but I need to be under 2ms. Sample data: [3][4][5][9] [2][8][9][4] [6][9][7][3] [5][8][8][2] The difference is: |4-2| + |5-6| + |9-5| + |9-9| + |4-8| + |3-8| = 2 + 1 + 4 + 0 + 4 + 5 = 16 In order to do that, I use the following algorithm: int i,j,result=0; for(i=0; i<4; i++) for(j=0; j<4; j++) result+=abs(array[i][j]-[j][i]); return result; But this algorithm keeps accessing the column, row, column, row, etc which make inefficient use of cache. Is there a way to improve my function?

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  • simple query Delete records in a table based on count logic

    - by user1905941
    a table with a pk and status column which is having values as 'Y','N','NULL' Query: get the count of records with status column as 'Y', if this count exceeds 1% of total count of records then dont delete , else delete the records in the table. i tried like this Declare v_count Number; v_count1 Number; BEGIN v_count := select count(*) from temp; v_count1 := select count(*) from temp where status = 'Y' ; v_count := v_count + ((0.1) * (v_count)) if (v_count1 > v_count) { insert into temp1 values(pk,status) } else { Delete from temp ; } END;

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  • LINQ to SQL, how to write a method which checks if a row exists when we have multiple tables

    - by Beles
    Hi, I'm trying to write a method in C# which can take as parameter a tabletype, column and a columnvalue and check if the got a row with a with value the method looks like: public object GetRecordFromDatabase(Type tabletype, string columnname, string columnvalue) I'm using LINQ to SQL and need to to this in a generic way so I don't need to write each table I got in the DB. I have been doing this so far for each table, but with more than 70 of these it becomes cumbersome and boring to do. Is there a way to generate the following code dynamically, And swap out the hardcoded tablenames with the values from the parameterlist? In this example I have a table in the DB named tbl_nation, which the DataContext pluralizes to tbl_nations, and I'm checking the column for the value if (DB.tbl_nations.Count(c => c.code.Equals(columnvalue)) == 1) { return DB.tbl_nations.Single(c => c.code.Equals(columnvalue)); }

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  • Problem decrementing in Java with '-='

    - by hanesjw
    I'm making a scrolling game on Android and am having a hard time figuring out why the code below does not decrement past 0. Objects start at the end of the screen (so the x position is equal to the width of the screen) the objects move accross the screen by decrementing their x positions. I want them to scroll off of the screen, but when the x position hits 0, the objects just stay at 0, they do not move into the negatives. Here is my code to move objects on the screen private void incrementPositions(long delta) { float incrementor = (delta / 1000F) * Globals.MAP_SECTION_SPEED; for(Map.Entry<Integer, HashMap<Integer, MapSection>> column : scrollingMap.entrySet()) { for(Map.Entry<Integer, MapSection> row : column.getValue().entrySet()) { MapSection section = row.getValue(); section.x -= incrementor; } } } It works ok if I change section.x -= incrementor; to section.x = section.x - (int)incrementor; but if i do that the scrolling doesn't appear as smooth.

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