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  • Best way to have unique key over 500M varchar(255) records in mysql/innodb?

    - by taw
    I have url column with unique key over it - but its performance on updates is absolutely atrocious. I suspect that's because the index doesn't all fit in memory. So I was thinking, how about adding a column of md5(url) with 16 bytes of binary data and unique-keying that instead. What would be the best datatype for that? I'd love to be able to just see 32-character hex hash, while mysql would convert it to/from 16 binary bytes and index that, as programs using the database might have some troubles with arbitrary binary data that I'd rather avoid if possible (also I'm a bit afraid that mysql might get some strange ideas about character sets and for example overalocating storage for that by 3:1 because it thinks it might need utf8, how do I avoid that for cure?).

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  • How can I ask Hibernate to create an index on a foreign key (JoinColumn)?

    - by Kent Chen
    Hi, This is my model. class User{ @CollectionOfElements @JoinTable(name = "user_type", joinColumns = @JoinColumn(name = "user_id")) @Column(name = "type", nullable = false) private List<String> types = new ArrayList<String>(); } You can imagin there would be a table called "user_type", which has two columns, one is "user_id", the other is "type". And when I use hbm2ddl to generate the ddls, I can have this table, along with the foreign key constraint on "user_id". However, there is no index of this for this column. And I need this index. How can I let hibernate to generate this index for me? Thank you!

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  • How to build a Drag and Dropable Tree using Jquery for Menu?

    - by Anil
    Hi all i want to build a Menu Builder with drag and drop which i am trying to do like here is the jsfiddle of what i am trying to do This and i want the functionality to be like This i will have all products list on a side and i should have a Add column button ,when i click on Add Column button a div should open where i should be able to drag and drop my products like the above the first product i drop in a div should be main then i should be able to add child to that particular product i should be able to add any number of submenus to it like this div1 Mens shoes SportShoes CasualShoe Shirts Casualshirts div2 Womens shoes SportShoes CasualShoe Shirts Casualshirts this is what i have to do can any one help me doing this please

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  • MySQL Query to receive random combinations from two tables.

    - by Michael
    Alright, here is my issue, I have two tables, one named firstnames and the other named lastnames. What I am trying to do here is to find 100 of the possible combinations from these names for test data. The firstnames table has 5494 entries in a single column, and the lastnames table has 88799 entries in a single column. The only query that I have been able to come up with that has some results is: select * from (select * from firstnames order by rand()) f LEFT JOIN (select * from lastnames order by rand()) l on 1=1 limit 10; The problem with this code is that it selects 1 firstname and gives every lastname that could go with it. While this is plausible, I will have to set the limit to 500000000 in order to get all the combinations possible without having only 20 first names(and I'd rather not kill my server). However, I only need 100 random generations of entries for test data, and I will not be able to get that with this code. Can anyone please give me any advice?

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  • Rails creating and updating 2 model records simultaneously

    - by LearnRails
    I have 2 tables product and history product table id name type price location 1 abc electronics $200 aisle1 history table id product_id status 1 1 price changed from $200 to $180 Whenever the product price or location is updated by a user by hitting the update button, 1) the changes should be automatically be reflected in the history status column without the user having to enter that manually. if the price is updated from 200 to 180 then a new history row will be created with new id and the status column will say ' price changed from $200 to $180' if the location is updated from aisle1 to aisle 2 then status displays ' loc changed from ailse1 to aisle 2' I tried to @product = Product.new(params[:product]) @history= History.new(params[:history]) if @product.save @history.new(attributes) == I am not sure of whether this approach is correct I would really appreciate if someone could tell me how the history can be automatically updated in this case.

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  • C# Same DataSource + Multiple DataGridViews = Data Binding Issues?

    - by C. Griffin
    Here's what I'm doing: I have (2) DataGridView controls DGV #1 is bound to the DataSet, DGV #2 is bound to a DataView of the SAME DataSet Now, what I'm needing to accomplish here is this: When a user checks a boolean column on the original DGV, the second DGV should now display the newly checked row also. The context is that the first DGV is a master list, and the second one is a "favorite" view of the first. When I check the rows, the favorite column does NOT update. Do I need to use a DataAdapter to actually update the database, or can I operate directly on the DataSet (DataTable) -- or even with the Rows in the original DataGridView?

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  • JSF Pass parameter to another page

    - by DD
    In JSF how do you pass a parameter from one page to another without using managed beans? e.g. <h:dataTable value="#{myObjects}" var="object"> <h:column> <h:commandButton value="View Object" action="view-object"/> </h:column> </h:dataTable> I want to pass the object so an the next page I can simply do #{object.displayValue} Thxs.

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  • SQL update statement to change the value of a field and not replace it

    - by wzzrd
    I'm in the process of migrating some databases. I have this table that has a couple of hundred rows, and has a filename column. To each record in this table, the filename column needs to be altered and part of a path needs to be prepended to the value that is in that field. The table is like: | 1 | filename1 | | 2 | filename2 | and needs to become: | 1 | path/filename1 | | 2 | path/filename2 | I am not an SQL guru, but I know the basics. This eludes me though. Is there a way to do something like: update table set filename = 'path/' + filename where id = 1;

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  • How do I specify a default value in a MS Access query?

    - by jheddings
    I have three tables similar to the following: tblInvoices: Number | Date | Customer tblInvDetails: Invoice | Quantity | Rate | Description tblPayments: Invoice | Date | Amount I have created a query called exInvDetails that adds an Amount column to tblInvDetails: SELECT tblInvDetails.*, [tblInvDetails.Quantity]*[tblInvDetails.Rate]* AS Amount FROM tblInvDetails; I then created a query exInvoices to add Total and Balance columns to tblInvoices: SELECT tblInvoices.*, (SELECT Sum(exInvDetails.Amount) FROM exInvDetails WHERE exInvDetails.Invoice = tblInvoices.Number) AS Total, (SELECT Sum(tblPayments.Amount) FROM tblPayments WHERE tblPayments.Invoice = tblInvoices.Number) AS Payments, (Total-Payments) AS Balance FROM tblInvoices; If there are no corresponding payments in tblPayments, the fields are null instead of 0. Is there a way to force the resulting query to put a 0 in this column?

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  • NSUserDefaults and show a picture

    - by Momeks
    Hi , iam using setting.bundle and i try to show a hidden picture with Switch toggle , here is my code but i miss something : NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [//Some code show the hidden pic]; myPic.hidden = NO; my key is .e.g = wood_back should i use ObjectForKey ?

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  • rewrite routes for URl

    - by user348173
    I have the following URl: http://localhost:12981/BaseEvent/EventOverview/12?type=Film This is route: routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults ); I want that in a browser the url looks like: http://localhost:12981/Film/Overview/12 How can I do this? One more example: http://localhost:12981/BaseEvent/EventOverview/15?type=Sport should be http://localhost:12981/Sport/Overview/15 Thanks.

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  • SQL Convert Nvarchar(255) to DateTime problem

    - by steven
    Hi, I'm using SQL server 2008. I have 2 Tables: Table 1 and Table 2. Table 1 has 1 column called: OldDate which is nvarchar(255), null Table 2 has 1 column called: NewDate which is datetime, not null Example data in Table 1: 26/07/03 NULL NULL 23/07/2003 7/26/2003 NULL 28/07/03 When i try CAST(OldDate as datetime) I get this error: Arithmetic overflow error converting expression to data type datetime. I need to insert OldDate into NewDate with no errors. I can't skip some rows. Anyhelp would be appreciated.

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  • How do I specify a dynamic position for the start of substring?

    - by analyticsPierce
    As in the example, I am trying to substring the Video_full column in a data.frame (video_data_2) I am working on. I want to keep all the characters after the period. The period is always present, there is only one period and it is in a different position in each value for the column. Date Video_full Instances 1 Apr 1, 2010 installs/AA.intro_video_1 546 2 Apr 1, 2010 installs/ABAC.intro_video_2 548 I got substring to work; video_data_2$Video_full <- substring(video_data_2$Video_full,11) And strsplit also; strsplit("installs/AA.intro_video_1 ",'[.]') I'm just not able to figure out how to start the substring in a dynamic position or only keep the second value returned by strsplit. Thanks for any help you can offer for a simple question.

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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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  • 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 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 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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  • 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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  • 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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  • 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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