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  • Get the first and last posts in a thread

    - by Grampa
    I am trying to code a forum website and I want to display a list of threads. Each thread should be accompanied by info about the first post (the "head" of the thread) as well as the last. My current database structure is the following: threads table: id - int, PK, not NULL, auto-increment name - varchar(255) posts table: id - int, PK, not NULL, auto-increment thread_id - FK for threads The tables have other fields as well, but they are not relevant for the query. I am interested in querying threads and somehow JOINing with posts so that I obtain both the first and last post for each thread in a single query (with no subqueries). So far I am able to do it using multiple queries, and I have defined the first post as being: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id LIMIT 0, 1 The last post is pretty much the same except for ORDER BY id DESC. Now, I could select multiple threads with their first or last posts, by doing: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id GROUP BY t.id But of course I can't get both at once, since I would need to sort both ASC and DESC at the same time. What is the solution here? Is it even possible to use a single query? Is there any way I could change the structure of my tables to facilitate this? If this is not doable, then what tips could you give me to improve the query performance in this particular situation?

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  • How to check with PHP does a SQL database already have

    - by Dan Horvat
    I've tried to find the answer to this question but none of the answers fit. I have two databases, one has 15.000.000 entries and I want to extract the necessary data and store it in a much smaller database with around 33.000 entries. Both databases are open at the same time. Or at least they should be. While having the big database open and extracting the entries from it, is it possible to check whether the value already exists in the smaller database? I just need some generic way which checks that.

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  • Partioning the Table into .net - Creating columner database.

    - by Omky
    Hello Geeks, I am developing some tool for BI. There are terms like Fact, Dimensions and Measures. My application will connect to the normal database and read the data from that table. Now, I want to convert all this data into columnar database. That is all the columns from this table will be transfer into 3 tables each. Consider below table:- ID Product 1 XYZ 2 ABC 3 ABC Now, I want to convert the Product column i.e. dimension into 3 tables. dim_product_table:- ID Product 1 XYZ 2 ABC dim_product_fmk(fact map by key):- Where we will store key-value pair of Key Row 1 1 1 2 2 3 dim_product_fmr(fact map by row):- The above table will be reversed. Row Key 1 1 2 1 3 2 The another requirement is all above table should be generated dynamically and I should be able to JOIN all those. Can anybody help me? Thanks in advance.

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  • Selecting records with specific month and year in SQL Server 2005

    - by John
    I want to list records with a particular month and year. The table name is 'Arrival' and 'date' is the field that stores the date that the record was added. This is to be done from a C# application. For example, if the user selects month as 'April' and year as '2009' in the application, it will list all the records that were added on April,2009. (I only need the query, hope I can figure out the rest :) )

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  • JQuery Onclick display selected info

    - by Emily
    I want to display the selected price, category and size on the dropdown slideingDiv. But what I have done below is not working. I have try to echo out to see if the data have been sent thought but I got nothing. Is anything wrong with my code? Script <script type="text/javascript"> $(document).ready(function () { $(".slidingDiv").hide(); $(".show_hide").show(); $('.show_hide').click(function () { $(".slidingDiv").slideToggle(); }); }); </script> Button <button a href="product.php?ProdID=<?php echo $id; ?>" class="show_hide" id="button" name="button">Add to cart</a></button> PHP <div class="slidingDiv"> <?php dbconnect(); $pid = $_POST['pid']; $length = $_POST["size"]; $qty = $_POST['Qty']; $Category = $_POST['Category']; $stmt4 = $conn->prepare(" SELECT Product.Name as ProductName, Category.Name, size, Price FROM item_Product, Product, Category WHERE Product.ProdID =:pid AND size= :length AND Category.Name = :Category Limit 1"); $stmt4->bindParam('pid',$pid); $stmt4->bindParam('length',$length); $stmt4->bindParam('Category',$Category); $stmt4->execute(); foreach ($stmt4->fetchAll(PDO::FETCH_ASSOC) as $row4 ) { $product_name = $row4["ProductName"]; $price = $row4["Price"]; $length = $row4["size"]; $Category = $row4["Name"]; ?> Item was added shopping bag </br> Name:<?php echo $row4['ProductName']; ?> </br> Length:<?php echo $row4['size']; ?> </br> Category:<?php echo $row4['Name']; ?> </br> Price:<?php echo $row4['Price']; ?> </br> <?php } ?> <a href="cart.php">View Cart</a> </div>

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  • Does introducing foreign keys to MySQL reduce performance

    - by Tam
    I'm building Ruby on Rails 2.3.5 app. By default, Ruby on Rails doesn't provide foreign key contraints so I have to do it manually. I was wondering if introducing foreign keys reduces query performance on the database side enough to make it not worth doing. Performance in this case is my first priority as I can check for data consistency with code. What is your recommendation in general? do you recommend using foreign keys? and how do you suggest I should measure this?

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  • Cannot add an entity that already exists.

    - by mazhar
    Code: public ActionResult Create(Group group) { if (ModelState.IsValid) { group.int_CreatedBy = 1; group.dtm_CreatedDate = DateTime.Now; var Groups = Request["Groups"]; int GroupId = 0; GroupFeature GroupFeature=new GroupFeature(); foreach (var GroupIdd in Groups) { // GroupId = int.Parse(GroupIdd.ToString()); } var Features = Request["Features"]; int FeatureId = 0; int t = 0; int ids=0; string[] Feature = Features.Split(',').ToArray(); //foreach (var FeatureIdd in Features) for(int i=0; i<Feature.Length; i++) { if (int.TryParse(Feature[i].ToString(), out ids)) { GroupFeature.int_GroupId = 35; GroupFeature.int_FeaturesId = ids; if (ids != 0) { GroupFeatureRepository.Add(GroupFeature); GroupFeatureRepository.Save(); } } } return RedirectToAction("Details", new { id = group.int_GroupId }); } return View(); } I am getting an error here Cannot add an entity that already exists. at this line GroupFeatureRepository.Add(GroupFeature); GroupFeatureRepository.Save();

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  • Choosing between a union and a boolean condition

    - by bread
    Does this require a UNION? SELECT vend_id, prod_id, prod_price FROM products WHERE prod_price <= 5 UNION SELECT vend_id, prod_id, prod_price FROM products WHERE vend_id IN (1001,1002); Or is it the same if you do it this way? SELECT vend_id, prod_id, prod_price FROM products WHERE prod_price <= 5 OR vend_id IN (1001,1002);

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  • Error using iif in ms access query

    - by naveen
    I am trying to fire this query in MS Access SELECT file_number, IIF(invoice_type='Spent on Coding',SUM(CINT(invoice_amount)), 0) as CodingExpense FROM invoice GROUP BY file_number I am getting this error Error in list of function arguments: '=' not recognized. Unable to parse query text. I tried replacing IIF with SWITCH to no avail. What's wrong with my query and how to correct this?

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  • How do I select a fixed number of rows for each group?

    - by Maiasaura
    Here is some example data in a mysql table a b distance 15 44 250 94 31 250 30 41 250 6 1 250 95 18 250 72 84 500 14 23 500 55 24 500 95 8 500 59 25 500 40 73 500 65 85 500 32 50 500 31 39 500 22 25 500 37 11 750 98 39 750 15 57 750 9 22 750 14 44 750 69 22 750 62 50 750 89 35 750 67 65 750 74 37 750 52 36 750 66 53 750 82 74 1000 79 22 1000 98 41 1000 How do I query this table such that I get 2 rows per distance selected at random? A successful query will produce something like a b distance 30 41 250 95 18 250 59 25 500 65 85 500 15 57 750 89 35 750 79 22 1000 98 41 1000

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  • MySQL Insert Data Question

    - by Nano HE
    Hi, assume I already created a table in MySQL as below CREATE TABLE IF NOT EXISTS `sales` ( `id` smallint(5) unsigned NOT NULL auto_increment, `client_id` smallint(5) unsigned NOT NULL, `order_time` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP, `sub_total` decimal(8,2) NOT NULL, `shipping_cost` decimal(8,2) NOT NULL, `total_cost` decimal(8,2) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=9 ; -- -- Dumping data for table `sales` -- If I added a new field must_fill for the current table. `must_fill` tinyint(1) unsigned NOT NULL, User can insert less than the number of fiels items to the table defaultly, just as the script of below. INSERT INTO `sales` (`id`, `client_id`, `order_time`, `sub_total`, `shipping_cost`, `total_cost`) VALUES (8, 12312, '2007-12-19 01:30:45', 10.75, 3.00, 13.75); It's fine. But How can I configure the field (must_fill) to a MUST INCLUDE Data field when user plan to insert into new data. BTW, The code will be integrated in PHP script.

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  • Arranging VS2008 generated LinqToSql/EntityFramework data models/contexts in assemblies.

    - by JMSA
    What pattern should I use for data-access in case of VS2008 generated L2s or EF DataModels? Repository-pattern or what? As we know VS2008 generates Data-Models and DataContexts/ObjectContexts in the same file, then, how should I arrange my VS2008 assemblies in my VS2008 solution to achieve a layered design? If I use repository pattern, how should I arrange my assemblies in the VS2008 solution (as Data-Models and Data/Object-Contexts are stored in the same file...)? Any web/example link would be appreciated.

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  • How do I drop a foerign key in mssql?

    - by mmattax
    I have created a foreign key (in mssql / tsql) by: alter table company add CountryID varchar(3); alter table company add constraint Company_CountryID_FK foreign key(CountryID) references Country; I then run this query: alter table company drop column CountryID; and I get this error: Msg 5074, Level 16, State 4, Line 2 The object 'Company_CountryID_FK' is dependent on column 'CountryID'. Msg 4922, Level 16, State 9, Line 2 ALTER TABLE DROP COLUMN CountryID failed because one or more objects access this column. I have tried this, yet it does not seem to work: alter table company drop foreign key Company_CountryID_FK; alter table company drop column CountryID; What do I need to do to drop the CountryID column? Thanks.

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  • How to write contents of a rails database to external file

    - by user1296787
    I'm trying to have rails send the contents of my database to an external textfile. I wanted this done everytime a new user is created. However, when i try to do the following in my user.rb model file, before_save :write_data def write_data() File.open("data.txt", "w") do |myfile| myfile.write(User.all) end end It doesn't write the actual contents of the database, instead, it displays something like this User:0x109858540 Can anyone help? Thanks.

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  • DateTime in SqlServer VisualStudio C#

    - by menacheb
    Hi, I Have a DataBase in my project With Table named 'ProcessData' and columns named 'Start_At' (Type: DateTime) and 'End_At' (Type: DateTime) . When I try to enter a new record into this table, it enter the data in the following format: 'YYYY/MM/DD HH:mm', when I actualy want it to be in that format: 'YYYY/MM/DD HH:mm:ss' (the secondes dosen't apper). Does anyone know why, and what should I do in order to fix this? Here is the code I using: con = new SqlConnection("...."); String startAt = "20100413 11:05:28"; String endAt = "20100414 11:05:28"; ... con.Open();//open the connection, in order to get access to the database SqlCommand command = new SqlCommand("insert into ProcessData (Start_At, End_At) values('" + startAt + "','" + endAt + "')", con); command.ExecuteNonQuery();//execute the 'insert' query. con.Close(); Many thanks

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  • Why is doing a top(1) on an indexed column in mssql slow?

    - by reinier
    I'm puzzled by the following. I have a DB with around 10 million rows, and (among other indices) on 1 column is an index. Now I have 700k rows where the campaignid is indeed 3835 For all these rows, the connectionid is the same. I just want to find out this connectionid. use messaging_db; SELECT TOP (1) connectionid FROM outgoing_messages WITH (NOLOCK) WHERE (campaignid_int = 3835) Now this query takes approx 30 seconds to perform! I (with my small db knowledge) would expect that it would take any of the rows, and return me that connectionid If I test this same query for a campaign which only has 1 entry, it goes really fast. So the index works. How would I tackle this and why does this not work?

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  • Designing a table to store EXIF data

    - by rafale
    I'm looking to get the best performance out of querying a table containing EXIF data. The queries in question will only search the EXIF data for the specified strings and return the row index on a match. With that said, would it better to store the EXIF data in a table with separate columns for each of the tags, or would storing all of the tags in a single column as one long delimited string suit me just as well? There are around 115 EXIF tags I'll be storing, and each record would be around 1500 to 2000 chars in length if concatenated into a single string.

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  • Find Date From Non Contiguous Ranges

    - by AGoodDisplayName
    I am looking to find an best way to find a date from date ranges that may or may not be contiguous (I am trying to avoid a cursor, or a heavy function if possible). Lets say I have hotel guests that come and go (check in, check out). I want to find the date that a certain guest stayed their 45th night with us. The database we use records the data as so: Create Table #GuestLog( ClientId int, StartDate DateTime, EndDate DateTime) Here is some data Insert Into #GuestLog Values(1, '01/01/2010', '01/10/2010') Insert Into #GuestLog Values(1, '01/16/2010', '01/29/2010') Insert Into #GuestLog Values(1, '02/13/2010', '02/26/2010') Insert Into #GuestLog Values(1, '04/05/2010', '06/01/2010') Insert Into #GuestLog Values(1, '07/01/2010', '07/21/2010') So far I can only think of solutions that involve functions with temp tables and crazy stuff like that, I feel like I'm over thinking it. Thanks ahead of time.

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  • how to write this query using joins?

    - by aquero
    Hi, i have a table campaign which has details of campaign mails sent. campaign_table: campaign_id campaign_name flag 1 test1 1 2 test2 1 3 test3 0 another table campaign activity which has details of campaign activities. campaign_activity: campaign_id is_clicked is_opened 1 0 1 1 1 0 2 0 1 2 1 0 I want to get all campaigns with flag value 3 and the number of is_clicked columns with value 1 and number of columns with is_opened value 1 in a single query. ie. campaign_id campaign_name numberofclicks numberofopens 1 test1 1 1 2 test2 1 1 I did this using sub-query with the query: select c.campaign_id,c.campaign_name, (SELECT count(campaign_id) from campaign_activity WHERE campaign_id=c.id AND is_clicked=1) as numberofclicks, (SELECT count(campaign_id) from campaign_activity WHERE campaign_id=c.id AND is_clicked=1) as numberofopens FROM campaign c WHERE c.flag=1 But people say that using sub-queries are not a good coding convention and you have to use join instead of sub-queries. But i don't know how to get the same result using join. I consulted with some of my colleagues and they are saying that its not possible to use join in this situation. Is it possible to get the same result using joins? if yes, please tell me how.

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  • Calculate open timeslots given availability and existing appointments - by day

    - by Andre
    Overview: I have a table which stores a persons "availability" for a current day, e.g. Mon - 8:00am - 11:30am Mon - 1:30pm - 6:00pm A second table stores appointments that this person already has for the same day, e.g. Mon - 8:30am - 11:00am Mon - 2:30pm - 4pm Desired result: Doing calculationsI'd like to have the following result - e.g. "this person has availability on the given day": Mon - 8:00am - 8:30am Mon - 11:00am - 11:30am Mon - 1:30pm - 2:30pm Mon - 4:00pm - 6:00pm Any ideas on how to calculate the output given the two inputs (e.g. availability, existing appointments) would be greatly appreciated. Preferably I'd use javascript on the client to do the calculating as I would believe that doing it within the DB (I'm using MSSQL) would be slow for many records, persons, etc. Hope this is enough information to illustrate the problem at hand - Many thanks in advance.

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  • Migrating from mssql to firebird: pro and cons

    - by user193655
    i am considering the migration for 3 reasons: 1) SQLSERVER installation is a nightmar, expecially for 1-user software. Software installs in 10 seconds, SQLServer in 1 hour. Firebird installation is much easier. 2) SQLSERVER runs on windows server only 3) My customers have all the express edition 4) i am not using any advanced feature, I am now starting using filestream, but the main reason for this is that Express eidtion has 4/10GB db size limit So these are all Pros of moving to Firebird. Which are the cons? I can also plan to support both platiforms, but this will backfire I fear.

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  • why datetime.now not work when I didn't use tolist?

    - by MemoryLeak
    When I use datacontext.News .Where(p => p.status == true) .Where(p => p.date <= DateTime.Now) .ToList(); the system will return no results; When I use datacontext.News .Where(p => p.status == true) .ToList() .Where(p => p.date <= DateTime.Now) .ToList(); system will return expected results. Can anyone tell me what's up? Thanks in advance !

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  • How do I do proximity search in Oracle right?

    - by hko19
    Oracle's NEAR operator for full text search returns a score based on the proximity of two or more query terms. For example: near((dog, bite), 6) matches if 'dog' and 'bite' occurs within 6 words. What if I'd like it to match if either 'dog' or 'cat' or any other type of animal occurs within 6 words of the word 'bite'? I tried: near(((dog OR cat OR animal), bite), 6) but I got: NEAR operand not a phrase, equivalence or another NEAR expression Rather than expanding all possible combination into multiple NEAR and 'or' them together, what is the proper way to write such query?

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