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• Query Access and VB.NET

  - by yae

  Hi all: I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are vinculated with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obatin the price of the main product, but not runs. This query not returns any value SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5));

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• Can't return a List from a Compiled Query.

  - by Andrew

  I was speeding up my app by using compiled queries for queries which were getting hit over and over. I tried to implement it like this: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id) End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, List(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ (From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u).ToList()) This did not work and I got this error message: Type : System.ArgumentNullException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 Message : Value cannot be null. Parameter name: value However, when I changed my compiled query to return IQueryable instead of List like so: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id).ToList() End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, IQueryable(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u) It worked fine. Can anyone shed any light as to why this is? BTW, compiled queries rock! They sped up my app by a factor of 2.

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• Help Me With This Access Query

  - by yae

  I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are related with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. "Products" table contains all products (p EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obatin the price of the main product, but not runs. This query not returns any value: SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5)); MORE INFO The table "products" contains all the products to sell that it is in the shop. The table "pieces" is to take a control of the compound products. To know those who are the products children. For example of compound product: computers. This product is composed by other products (motherboard, hard disk, memory, cpu, etc.)

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• SQL Query with multiple values in one column

  - by lp1

  I've been beating my head on the desk tring to figure this one out. I have a table that stores job information, and reasons for a job not being completed. The reasons are numeric,01,02,03,etc. You can have two reason for a pending job. If you select two reasons, they are stored in the same column, seperated by a comma. This is anExample from the JOBID table: Job_Number User_Assigned PendingInfo 1 user1 01,02 Now, there is another table named Pending, that stores what those values actually represent. 01=Not enough info, 02=Not enough time, 03=Waiting Review. Example: Pending_Num PendingWord 01 Not Enough Info 02 Not Enough Time What I'm trying to do is query the database to give me all the job numbers, users, pendinginfo, and pending reason. I can break out the first value, but can't figure out how to do the second. What my limited skills have so far: *select Job_number,user_assigned,SUBSTRING(pendinginfo,0,3),pendingword from jobid,pending where SUBSTRING(pendinginfo,0,3)=pending.pending_num and pendinginfo!='00,00' and pendinginfo!='NULL'* What I would like to see for this example would be: Job_Number User_Assigned PendingInfo PendingWord PendingInfo PendingWord 1 User1 01 Not Enough Info 02 Not Enough Time Thanks in advance

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• XPATH Query: How to get two elements?

  - by Damiano

  Hello My HTML code is: <table> <tr> <td class="data1"><p>1</td></td> <td class="data1"><p>2</td></td> <td class="data1"><p>3</td></td> <td class="data1"><p>4</td></td> </tr> <tr> <td class="data1"><p>5</td></td> <td class="data1"><p>6</td></td> <td class="data1"><p>7</td></td> <td class="data1"><p>8</td></td> </tr> </table> My query is: xpath='//tr//td[@class="data1"][4]/p' The results is: <p>4</p> <p>8</p> The results is correct! but, if I want to get example: <p>3</p> <p>4</p> <p>7</p> <p>8</p> So [3]/p and [4]/p How to get these two elements each <tr> ? Thank you so much!

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• Please help optimizing a long running query (left outer join, with 2 subqueries)

  - by 46and2

  Hi all. The query I need help with is: SELECT d.bn, d.4700, d.4500, ... , p.`Activity Description` FROM ( SELECT temp.bn, temp.4700, temp.4500, .... FROM `tdata` temp GROUP BY temp.bn HAVING (COUNT(temp.bn) = 1) ) d LEFT OUTER JOIN ( SELECT temp2.bn, max(temp2.FPE) AS max_fpe, temp2.`Activity Description` FROM `pdata` temp2 GROUP BY temp2.bn ) p ON p.bn = d.bn; The ... represents other fields that aren't really important to solving this problem. The issue is on the the second subquery - it is not using the index I have created and I am not sure why, it seems to be because of the way TEXT fields are handled. The first subquery uses the index I have created and runs quite snappy, however an explain on the second shows a 'Using temporary; Using filesort'. Please see the indexes I have created in the below table create statements. Can anyone help me optimize this? By way of quick explanation the first subquery is meant to only select records that have unique bn's, the second, while it looks a bit wacky (with the max function there which is not being used in the result set) is making sure that only one record from the right part of the join is included in the result set. My table create statements are CREATE TABLE `tdata` ( `BN` varchar(15) DEFAULT NULL, `4000` varchar(3) DEFAULT NULL, `5800` varchar(3) DEFAULT NULL, .... KEY `BN` (`BN`), KEY `idx_t3010`(`BN`,`4700`,`4500`,`4510`,`4520`,`4530`,`4570`,`4950`,`5000`,`5010`,`5020`,`5050`,`5060`,`5070`,`5100`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 CREATE TABLE `pdata` ( `BN` varchar(15) DEFAULT NULL, `FPE` datetime DEFAULT NULL, `Activity Description` text, .... KEY `BN` (`BN`), KEY `idx_programs_2009` (`BN`,`FPE`,`Activity Description`(100)) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 Thanks!

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• Complex SQL query, one to many relationship

  - by Ethan

  Hey SO, I have a query such that I need to get A specific dog All comments relating to that dog The user who posted each comment All links to images of the dog the user who posted each link I've tried a several things, and can't figure out quite how to work it. Here's what I have (condensed so you don't have to wade through it all): SELECT s.dog_id, s.name, c.comment, c.date_added AS comment_date_added, u.username AS comment_username, u.user_id AS comment_user_id, l.link AS link, l.date_added AS link_date_added, u2.username AS link_username, u2.user_id AS link_user_id FROM dogs AS d LEFT JOIN comments AS c ON c.dog_id = d.dog_id LEFT JOIN users AS u ON c.user_id = u.user_id LEFT JOIN links AS l ON l.dog_id = d.dog_id LEFT JOIN users AS u2 ON l.user_id = u2.user_id WHERE d.dog_id = '1' It's sorta close to working, but it'll only return me the first comment, and the first link all as one big array with all the info i requested. The are multiple comments and links per dog, so I need it to give me all the comments and all the links. Ideally it'd return an object with dog_id, name, comments(an array of the comments), links(an array of the links) and then comments would have a bunch of comments, date_added, username, and user_id and links would have a bunch of links with link, date_added, username and user_id. It's got to work even if there are no links or comments. I learned the basics of mySQL somewhat recently, but this is pretty far over my head. Any help would be wonderful. Thanks!

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• Overlap of the variable in mysql, my column are set to my query result

  - by foodil

  The question is not clear , let me clarify it: try{ $sql = ' SELECT UserID <==== (***********Used here for query ******) FROM user WHERE Rights != ?'; $stmt = $conn->prepare($sql); $stmt->execute(array('admin')); $result= $stmt->fetchAll(); } catch(PDOException $e) { die ($e->getMessage().'<a href="add.php"> Back</a>'); } foreach ($result as $set) { if ($set['UserID']==$_SESSION['username']) $rights='edit'; else {$rights=$_POST[$set['UserID']];} if (($rights != 'default' || $set['UserID']==$_SESSION['username']) && $_POST['public']==0 ) { $user=$set['UserID']; try { $query="INSERT INTO user_list(UserID <==== (***********Used here for insert ******),ListID,UserRights) VALUES ($user,$lastID,$rights)"; $stmt = $conn->prepare($query); $stmt->execute(); } catch(PDOException $e) { die ($e->getMessage().'<a href="add.php"> Back</a>'); $conn->rollBack(); } } } As you can see the UserID is a query result but it is also the column i need to insert, so when i insert into the table it will casued an error SQLSTATE[42S22]: Column not found: 1054 Unknown column 'UserA_ID' in 'field list' because the column is modify by my query result from: $query="INSERT INTO user_list(UserID,ListID,UserRights) VALUES ($user,$lastID,$rights)"; to: $query="INSERT INTO user_list(query_result_id,ListID,UserRights) VALUES ($user,$lastID,$rights)"; How to fix it ?Thank you.

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• Web page database query optimization

  - by morpheous

  I am putting together a web page which is quite 'expensive' in terms of database hits. I don't want to start optimizing at this stage - though with me trying to hit a deadline, I may end up not optimizing at all. Currently the page requires 18 (that's right eighteen) hits to the db. I am already using joins, and some of the queries are UNIONed to minimize the trips to the db. My local dev machine can handle this (page is not slow) however, I feel if I release this into the wild, the number of queries will quickly overwhelm my database (MySQL). I could always use memcache or something similar, but I would much rather continue with my other dev work that needs to be completed before the deadline - at least retrieving the page works - its simply a matter of optimization now (if required). My question therefore is - is 18 db queries for a single page retrieval completely outrageous - (i.e. I should put everything on hold and optimize the hell of the retrieval logic), or shall I continue as normal, meet the deadline and release on schedule and see what happens? [Edit] Just to clarify, I have already done the 'obvious' things like using (single and composite) indexes for fields used in the queries. What I haven't yet done is to run a query analyzer to see if my indexes etc are optimal.

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• MySQL query pulling from two tables, display in correct fields

  - by Matt Nathanson

  I'm trying to select all fields in two separate tables as long as they're sharing a common ID. //mysql query $result = mysql_query("SELECT * FROM project, links WHERE project.id = links.id and project.id = $clientID") //displaying the link if ($row['url'] != null){ echo "<div class='clientsection' id='links'>Links</div>"; echo "<a class='clientlink' id='link1' href='" . $row['url'] . "'>" . $row['name'] . "</a>"; } else { echo "<a class='clientlink' id='link1' href='" . $row['url'] . "' style='display:none;'>" . $row['name'] . "</a>"; }; As you can see, my tables are "projects", and "links" Each is sharing a common field "id" for reference. It looks as though where both links.id and project.id are equal, it outputs anything, but when there is no links.id associated with a given $clientID the container relative to the $clientID doesn't display at all. Essentially I'm using this to add links dynamically to a specific client in this CMS and if there are no links, I want the container to show up anyway. Hopefully I've expressed myself clearly, any pointers in the right direction are appreciated. Thanks!

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• MYSQL DELETE from a table [closed]

  - by Hossein

  Possible Duplicate: MySQL DELETE in a single table Hi, I have this table: userurltag(id,user,Url,tag) I want to remove rows that contain urls that are used by only one user, can someone help me? It seems that DELETE...(SELECT...) is not supported in Mysql.

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• SQL query for selecting the firsts in a series by cloumn

  - by SP

  I'm having some trouble coming up with a query for what I am trying to do. I've got a table we'll call 'Movements' with the following columns: RecID(Key), Element(f-key), Time(datetime), Room(int) The table is holding a history of Movements for the Elements. One record contains the element the record is for, the time of the recorded location, and the room it was in at that time. What I would like are all records that indicate that an Element entered a room. That would mean the first (by time) entry for any element in a series of movements for that element in the same room. The input is a room number and a time. IE, I would like all of the records indicating that any Element entered room X after time Y. The closest I came was this Select Element, min(Time) from Movements where Time > Y and Room = x group by Element This will only give me one room entry record per Element though (If the Element has entered the room X twice since time Y I'll only get the first one back) Any ideas? Let me know if I have not explained this clearly. I'm using MS SQLServer 2005.

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• NHibernate complex order query

  - by manu08

  Here's my simplified domain public class Notification { public Guid ID { get; set; } public string Name { get; set; } public IEnumerable<Location> Locations { get; set; } } public class Location { public Guid Id { get; set; } public string Name { get; set; } public decimal Longitude { get; set; } public decimal Latitude { get; set; } } Notifications and Locations have a many-to-many relationship (defined in table LocationsOnNotification). What I'd like to do is query for the nearest 10 Notifications from a given longitude and latitude. I've been trying to use ICriteria, but I'm not sure how to specify the ordering correctly: return Session.CreateCriteria<Notification>() .SetFirstResult(firstIndex) .SetMaxResults(maxResults) .AddOrder(Order.Asc( WHAT GOES HERE! )) .List<Notification>(); What I've been thinking of so far is adding a formula property to the Location mapping; something like this: <property name='Distance' formula='lots of geometry'/> But I'm not sure if that can take in parameters (since I'd need to pass in the user's location to calculate the distance), plus I'm not sure how to specify it in the Order.Asc clause given that it's a property on a many-to-many association class. Any ideas? Or perhaps I should take a different approach altogether. Thanks in advance!

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• How do I write this MySQL query?

  - by CT

  I am working on an Asset DB using a lamp stack. In this example consider the following 5 tables: asset, server, laptop, desktop, software All tables have a primary key of id, which is a unique asset id. Every object has all asset attributes and then depending on type of asset has additional attributes in the corresponding table. If the type is a server, desktop or laptop it also has items in the software table. Here are the table create statements: // connect to mysql server and database "asset_db" mysql_connect("localhost", "asset_db", "asset_db") or die(mysql_error()); mysql_select_db("asset_db") or die(mysql_error()); // create asset table mysql_query("CREATE TABLE asset( id VARCHAR(50) PRIMARY KEY, company VARCHAR(50), location VARCHAR(50), purchase_date VARCHAR(50), purchase_order VARCHAR(50), value VARCHAR(50), type VARCHAR(50), notes VARCHAR(200))") or die(mysql_error()); echo "Asset Table Created.</br />"; // create software table mysql_query("CREATE TABLE software( id VARCHAR(50) PRIMARY KEY, software VARCHAR(50), license VARCHAR(50))") or die(mysql_error()); echo "Software Table Created.</br />"; // create laptop table mysql_query("CREATE TABLE laptop( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), serial_number VARCHAR(50), esc VARCHAR(50), user VARCHAR(50), prev_user VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Laptop Table Created.</br />"; // create desktop table mysql_query("CREATE TABLE desktop( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), serial_number VARCHAR(50), esc VARCHAR(50), user VARCHAR(50), prev_user VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Desktop Table Created.</br />"; // create server table mysql_query("CREATE TABLE server( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Server Table Created.</br />"; ?> How do I query the database so that if I search by id, I receive all related fields to that asset id? Thank you.

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• SQL Query Math Gymnastics

  - by keruilin

  I have two tables of concern here: users and race_weeks. User has many race_weeks, and race_week belongs to User. Therefore, user_id is a fk in the race_weeks table. I need to perform some challenging math on fields in the race_weeks table in order to return users with the most all-time points. Here are the fields that we need to manipulate in the race_weeks table. races_won (int) races_lost (int) races_tied (int) points_won (int, pos or neg) recordable_type(varchar, Robots can race, but we're only concerned about type 'User') Just so that you fully understand the business logic at work here, over the course of a week a user can participate in many races. The race_week record represents the summary results of the user's races for that week. A user is considered active for the week if races_won, races_lost, or races_tied is greater than 0. Otherwise the user is inactive. So here's what we need to do in our query in order to return users with the most points won (actually net_points_won): Calculate each user's net_points_won (not a field in the DB). To calculate net_points, you take (1000 * count_of_active_weeks) - sum(points__won). (Why 1000? Just imagine that every week the user is spotted a 1000 points to compete and enter races. We want to factor-out what we spot the user because the user could enter only one race for the week for 100 points, and be sitting on 900, which we would skew who actually EARNED the most points.) This one is a little convoluted, so let me know if I can clarify further.

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• SQL using sum to count results of multiple subqueries

  - by asdas

  I have a table with 2 columns: integer and var char. I am given only the integer values but need to do work on the var char (string) values. Given an integer, and a list of other integers (no overlap), I want to find the string for that single integer. Then I want to take that string and do the INSTR command with that string, and all the other strings for all the other integers. Then I want the sum of all the INSTR so the result is one number. So lets say I have int x, and list y=[y0, y1, y2]. I want to do 3 INSTR commands like SUM(INSTR(string for x, string for y0), INSTR(string for x, string for y1), INSTR(string for x, string for y2)) I think im going in the wrong direction, this is what I have. Im not good with sub queries. SELECT SUM ( SELECT INSTR ( SELECT string FROM pages WHERE int=? LIMIT 1, ( SELECT string FROM pages WHERE id=? OR id=? OR id=? LIMIT 3 ) ) )

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• Query broke down and left me stranded in the woods

  - by user1290323

  I am trying to execute a query that deletes all files from the images table that do not exist in the filters tables. I am skipping 3,500 of the latest files in the database as to sort of "Trim" the table back to 3,500 + "X" amount of records in the filters table. The filters table holds markers for the file, as well as the file id used in the images table. The code will run on a cron job. My Code: $sql = mysql_query("SELECT * FROM `images` ORDER BY `id` DESC") or die(mysql_error()); while($row = mysql_fetch_array($sql)){ $id = $row['id']; $file = $row['url']; $getId = mysql_query("SELECT `id` FROM `filter` WHERE `img_id` = '".$id."'") or die(mysql_error()); if(mysql_num_rows($getId) == 0){ $IdQue[] = $id; $FileQue[] = $file; } } for($i=3500; $i<$x; $i++){ mysql_query("DELETE FROM `images` WHERE id='".$IdQue[$i]."' LIMIT 1") or die("line 18".mysql_error()); unlink($FileQue[$i]) or die("file Not deleted"); } echo ($i-3500)." files deleted."; Output: 0 files deleted. Database contents: images table: 10,000 rows filters table: 63 rows Amount of rows in filters table that contain an images table id: 63 Execution time of php script: 4 seconds +/- 0.5 second Relevant DB structure TABLE: images id url etc... TABLE: filter id img_id (CONTAINS ID FROM images table) etc...

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• MySQL floating point comparison issues

  - by Sharief

  I ran into an issue by introducing floating point columns in the MySQL database schema that the comparisons on floating point values don't return the correct results always. 1 - 50.12 2 - 34.57 3 - 12.75 4 - ...(rest all less than 12.00) SELECT COUNT(*) FROM `users` WHERE `points` > "12.75" This returns me "3". I have read that the comparisons of floating point values in MySQL is a bad idea and decimal type is the better option. Do I have any hope of moving ahead with the float type and get the comparisons to work correctly?

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• 'LINQ query plan' horribly inefficient but 'Query Analyser query plan' is perfect for same SQL!

  - by Simon_Weaver

  I have a LINQ to SQL query that generates the following SQL : exec sp_executesql N'SELECT COUNT(*) AS [value] FROM [dbo].[SessionVisit] AS [t0] WHERE ([t0].[VisitedStore] = @p0) AND (NOT ([t0].[Bot] = 1)) AND ([t0].[SessionDate] > @p1)',N'@p0 int,@p1 datetime', @p0=1,@p1='2010-02-15 01:24:00' (This is the actual SQL taken from SQL Profiler on SQL Server 2008.) The query plan generated when I run this SQL from within Query Analyser is perfect. It uses an index containing VisitedStore, Bot, SessionDate. The query returns instantly. However when I run this from C# (with LINQ) a different query plan is used that is so inefficient it doesn't even return in 60 seconds. This query plan is trying to do a key lookup on the clustered primary key which contains a couple million rows. It has no chance of returning. What I just can't understand though is that the EXACT same SQL is being run - either from within LINQ or from within Query Analyser yet the query plan is different. I've ran the two queries many many times and they're now running in isolation from any other queries. The date is DateTime.Now.AddDays(-7), but I've even hardcoded that date to eliminate caching problems. Is there anything i can change in LINQ to SQL to affect the query plan or try to debug this further? I'm very very confused!

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• SQL Filter Multiple Tables Data

  - by Brad

  If it matters, I'm using Firebird 2.1 database. I have three tables, one with keywords, one with negative keywords, and the other with required keywords. I need to be able to filter the data so the output has just the keywords that meat the stipulation of not being in the negative keyword list, and IF there are any required words, then it will require the results to have those keywords in the end result. The tables are very similar, the field in the tables that I would be matching against are all called keyword. I don't know SQL very well at all. I'm guessing it would be something like SELECT keyword from keywordstable where keyword in requiredkeywordstable and where NOT in negativekeywordstable Just a side note, The required keywords table could be empty which would mean there are no required keywords. Any help would be appreciated. -Brad

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• Need to add WHERE condition to query

  - by Angel Carlson

  I am trying to modify edit_orders.php in Zen Cart. Hoping someone might be able to help me add a condition to a query. I need the queries below to specify that the items selected from TABLE_PRODUCTS_DESCRIPTION and TABLE_CATEGORIES_DESCRIPTION must have a language_id = 1. Would be so grateful for any help you could provide. // ############################################################################ // Get List of All Products // ############################################################################ //$result = zen_db_query("SELECT products_name, p.products_id, x.categories_name, ptc.categories_id FROM " . TABLE_PRODUCTS . " p LEFT JOIN " . TABLE_PRODUCTS_DESCRIPTION . " pd ON pd.products_id=p.products_id LEFT JOIN " . TABLE_PRODUCTS_TO_CATEGORIES . " ptc ON ptc.products_id=p.products_id LEFT JOIN " . TABLE_CATEGORIES_DESCRIPTION . " cd ON cd.categories_id=ptc.categories_id LEFT JOIN " . TABLE_CATEGORIES_DESCRIPTION . " x ON x.categories_id=ptc.categories_id ORDER BY categories_id"); $result = $db -> Execute("SELECT products_name, p.products_id, categories_name, ptc.categories_id FROM " . TABLE_PRODUCTS . " p LEFT JOIN " . TABLE_PRODUCTS_DESCRIPTION . " pd ON pd.products_id=p.products_id LEFT JOIN " . TABLE_PRODUCTS_TO_CATEGORIES . " ptc ON ptc.products_id=p.products_id LEFT JOIN " . TABLE_CATEGORIES_DESCRIPTION . " cd ON cd.categories_id=ptc.categories_id ORDER BY categories_name");

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• Rails/mysql SUM distinct records - optimization

  - by pepernik

  Hey. How would you optimize this SQL SELECT SUM(tmp.cost) FROM ( SELECT DISTINCT clients.id as client, countries.credits_cost AS cost FROM countries INNER JOIN clients ON clients.country_id = countries.id INNER JOIN clients_groups ON clients_groups.client_id=clients.id WHERE clients_groups.group_id IN (1,2,3,4,5,6,7,8,9) GROUP BY clients.id ) AS tmp; I'm using this example as part of my Ruby on Rails project. Note that my nested SQL (tmp) can have more then 10 milion records. You can split that in more SQLs if the performance is better. Should I add any indexes to make it quicker (i have it on IDs)?

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• ClassCastException in iterating list returned by Query using Hibernate Query Language

  - by Tushar Paliwal

  I'm beginner in hibernate.I'm trying a simplest example using HQL but it generates exception at line 25 ClassCastException when i try to iterate list.When i try to cast the object returned by next() methode of iterator it generates the same problem.I could not identify the problem.Kindly give me solution of the problem. Employee.java package one; import javax.persistence.Entity; import javax.persistence.Id; @Entity public class Employee { @Id private Long id; private String name; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Employee(Long id, String name) { super(); this.id = id; this.name = name; } public Employee() { } } Main2.java package one; import java.util.Iterator; import java.util.List; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; public class Main2 { public static void main(String[] args) { SessionFactory sf=new Configuration().configure().buildSessionFactory(); Session s1=sf.openSession(); Query q=s1.createQuery("from Employee "); Transaction tx=s1.beginTransaction(); List l=q.list(); Iterator itr=l.iterator(); while(itr.hasNext()) { Object obj[]=(Object[])itr.next();//Line 25 for(Object temp:obj) { System.out.println(temp); } } tx.commit(); s1.close(); sf.close(); } }

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• Write a SQL to meet my requirement.

  - by rgksugan

  I have been trying to solve this problem for a lot of days. But wouldn't. Please help me. I need a SQL to list product_code, product_name, qty_sold, last_order_date for all the products that have been sold within a date range sorted by the number of quantity sold. My Table structure: tbl_product(product_id,product_code,product_name) tbl_order_detail(order_item_id,order_id,product_id,quantity) tbl_order(order_id,order_date)

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• Command Query Separation

  - by Liam McLennan

  Command query separation is a strategy, proposed by Bertrand Meyer, that each of an object’s methods should be either a command or a query. A command is an operation that changes the state of a system, and a query is an operation that returns a value. This is not the same thing as CQRS, hence why I think that CQRS is poorly named. An Example of Command Query Separation Consider a system that models books and shelves. There is a rule that a shelf may not be removed if it holds any books. One way to implement the removal is to write a method Shelf.Remove() that internally checks to make sure that the shelf is empty before removing it. If the shelf is not empty then it is not removed and an error is returned. To implement this feature following the principle of command query separation would require two methods, one to query the shelf and determine if it is empty and a second method to remove the shelf. Separating the query from the command makes the shelf class simpler to use because the state change is clear and explicit.

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