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  • How do I guarantee row uniqueness in MySQL without the use of a UNIQUE constraint?

    - by MalcomTucker
    Hi I have some fairly simple requirements but I'm not sure how I implement them: I have multiple concurrent threads running the same query The query supplies a 'string' value - if it exists in the table, the query should return the id of the matching row, if not the query should insert the 'string' value and return the last inserted id The 'string' column is (and must be) a text column (it's bigger than varchar 255) so I cannot set it as unique - uniqueness must be enforced through the access mechanism The query needs to be in stored procedure format (which doesnt support table locks in MySQL) How can I guarantee that 'string' is unique? How can I prevent other threads writing to the table after another thread has read it and found no matching 'string' item? Thanks for any advice..

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  • Remove specific string from multiple database rows in SQL

    - by Scott
    I have a column that contains page titles, which has the website name appended to the end of each. (e.g. Product Name | Company Name Inc.) I would like to remove the " | Company Name Inc." from multiple rows simultaneously. What SQl query commands (or query itself) would allow me to accomplish this? To re-illustrate, I want to convert multiple rows of 1 column from this: Product Name | Company Name Inc. To this: Product Name

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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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  • Find and sort by number of ocurrences of tag with Active Admin and act_as_taggable_on

    - by nunopolonia
    I'm using act_as_taggable_on and Active Admin on a Rails project. In that project there are Posts and each Post has Tags. I want to show a list of Tags in Active Admin and the number of ocurrences of each one. The way I found to do this was: index do column :name column :ocurrences do |tag| ocurrences = Post.tag_counts.find(tag.id).count end default_actions end Which will search the Tag List every time for every Post, which performance wise looks really bad. I would also like to be able to sort the tags by ocurrence. Any idea of how I can do it?

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  • read text files containing binary data as a single matrix in matlab

    - by user1716595
    I have a text file which contains binary data in the following manner: 00000000000000000000000000000000001011111111111111111111111111111111111111111111111111111111110000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111000111100000000000000000000000000000000 00000000000000000000000000000000000011111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000111111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000011111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111000111110000000000000000000000000000000 00000000000000000000000000000000000000111111111111111111111111111111111111111111111111111111110000000000000000000000000000000 00000000000000000000000000000000000000000000111111111111111111111111111111111111110000000011100000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111100111110000000000000000000000000000000 00000000000000000000000000000000000111111111111111111111111111111111111111111111111111110111110000000000000000000000000000000 00000000000000000000000000000000001111111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000000001111111111111111111111111111111111111111111111000011100000000000000000000000000000000 00000000000000000000000000000000000000001111111111111111111111111111111111111111111111000011100000000000000000000000000000000 00000000000000000000000000000000000001111111111111111111111111111111111111111111111111111111000000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111110000011100000000000000000000000000000000 00000000000000000000000000000000000000000000011111111111111111111111111111111111100000000011100000000000000000000000000000000 00000000000000000000000000000000000000111111111111111111111111111111111111111111111111110111100000000000000000000000000000000 Plz note that each 1 or 0 is independent i.e the values are not decimal.I need to find the column wise sum of the file.There are 125 columns in all (here it is jumping onto the next line) and there are 840946 rows. I have tried textread,fscanf and a few other matlab commands but the result is that they all read each row in decimal format and create a 840946*1 array.I want to create a 840946*125 array to compute a column wise sum. Kindly help, Thanks!

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  • Getting time from a cell in Google Spreadsheet

    - by lostInTransit
    Hi I have created a Google Spreadsheet form in which for one of the fields I get the time (hh:mm:ss) in 24-hour format. I am using Google Apps Scripts to read values from this spreadsheet and put it into another file. But the other file gets the entire date (don't know from where) and shows a date from 1899. Also the time is shown in PDT (not my time zone). Even the time it prints is not correct How do I read the column value as a string and put it in the other file OR get just the time from the column value (and the correct time) I am using a simple row[0][3] to get the values from an array after doing range.getValues() Thanks.

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  • 'cross-referencing' DataTable's

    - by Lee
    I have a DataGridView that is being filled with data from a table. Inside this table is a column called 'group' that has the ID of an individual group in another table. What I would like to do, is when the DataGridView is filled, instead of showing the ID contained in 'group', I'd like it to display the name of the group. Is there some type of VB.net 'magic' that can do this, or do I need to cross-reference the data myself? Here is a breakdown of what the 2 tables look like: table1 id group (this holds the value of column id in table 2) weight last_update table2 id description (this is what I would like to be displayed in the DGV.) BTW - I am using Visual Studio Express.

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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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  • Sql-server Database query help

    - by menacheb
    Hi, I have a problem that I didn't manage to solve for a very long time, and I quite desperate. I have a Database (SQL Server) with table named 'ProcessData' and columns named 'Process_Name' (Data Type: nvarchar(50)), 'Start_At' (DataType: DateTime) and 'End_At' (Data Type: DateTime). I need to know for each 'Time-Interval' (let's say 1 minute) how many processes (Process_Name = PN) was open (after or equal to the 'Start_at' column and before or equal to the 'End_At' column) during this time (It can be a few rows with the same data). Does anyone know how to make this query without a 'for' loop? (It ITSELF will promote the time), (The answer will be a table with two columns (1. The time the check took place. 2. the number of open processes at this time.) and a row for each 'Time-Interval' (1 minute in this example ) Many thanks,

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  • Can I bypass an intermediate object in hibernate

    - by Jherico
    I have top level entities TRACK, MEDIA_GROUP and MEDIA, each with an integer primary key. I also have a join table from TRACK to MEDIA_GROUP which is 1:1 and MEDIA has a FK column into MEDIA_GROUP. I'm trying to find a way in hibernate to map a collection of Media directly into the Track object, bypassing the creation of a MediaGroup object. Basically I want to turn this: TRACK <-> MEDIA_TRACK_MAP <-> MEDIA_GROUP <-> MEDIA into this: TRACK <-> MEDIA_TRACK_MAP <-> MEDIA But the join column between MEDIA_TRACK_MAP and MEDIA isn't the primary key of MEDIA.

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  • How can I do a 'where' clause in Linux shell?

    - by Hoa
    I have a CSV file and I would like to filter all the lines where the 19th column has two or more characters. I know the individual pieces but can't figure out how to glue them together. First I have to cat the file. The following prints the 19th column awk -F "," '{print $19}' file.txt awk also has length and ifs And I know it all has to be glued together using pipes. I'm just getting stuck at the exact syntax since I have not done much bash programming before.

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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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  • Handling null values with PowerShell dates

    - by Tim Ferrill
    I'm working on a module to pull data from Oracle into a PowerShell data table, so I can automate some analysis and perform various actions based on the results. Everything seems to be working, and I'm casting columns into specific types based on the column type in Oracle. The problem I'm having has to do with null dates. I can't seem to find a good way to capture that a date column in Oracle has a null value. Is there any way to cast a [datetime] as null or empty?

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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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  • 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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  • How to get the right row in a sorted DataView?

    - by ZeissS
    Hi, I have a DataGrid containing a small table. Until now, I had a double click handler on this grid which iterated over all rows to find the selected one: DataTable table = (DataTable)this.dataGrid.DataSource; int selectedRow = -1; for (int i=0; i<table.Rows.Count; i++) if (this.dataGrid.IsSelected(i)) selectedRow = i; break; } if ( selectedRow != -1 ) { DataRow row = table.Rows[selectedRow]; // More code ... } Problem: When the user clicks on a column header and sort the table, table.Rows does not return the right rows. It still contains the unsorted rows. How can I get the right column?

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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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  • 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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  • 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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  • 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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  • 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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