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• Select * from 'many to many' SQL relationship

  - by Rampant Creative Group

  I'm still learning SQL and my brain is having a hard time with this one. Say I have 3 tables: teams players and teams_players as my link table All I want to do is run a query to get each team and the players on them. I tried this: SELECT * FROM teams INNER JOIN teams_players ON teams.id = teams_players.team_id INNER JOIN players ON teams_players.player_id = players.id But it returned a separate row for each player on each team. Is JOIN the right way to do it or should I be doing something else? ----------------------------------------- Edit Ok, so from what I'm hearing, this isn't necessarily a bad way to do it. I'll just have to group the data by team while I'm doing my loop. I have not yet tried the modified SQL statements provided, but I will today and get back to you. To answer the question about structure - I guess I wasn't thinking about the returned row structure which is part of what lead to my confusion. In this particular case, each team is limited to 4 players (or less) so I guess the structure that would be helpful to me is something like the following: teams.id, teams.name, players.id, players.name, players.id, players.name, players.id, players.name, players.id, players.name, 1 Team ABC 1 Jim 2 Bob 3 Ned 4 Roy 2 Team XYZ 2 Bob 3 Ned 5 Ralph 6 Tom

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• Associate new Authlogic Model to existing Models

  - by BriteLite

  Hello, While playing around with Rails (since I am a newbie) while reading Agile Rails book I came across an issue using the Gem Authlogic that I don't know how to address. I have a simple business Model. The tables store the following information: Name, Address, Latitude, and Longitude. The above approach has been working fine, because using the console I can enter the information and it shows up, where I need it to. My issue now is that I want to add authentication to it. As in assign those records in the table, to individual accounts. Since Authlogic is an authentication gem, can this be done? What I am trying to get to here is that, I enter a few records and leave it at that. Few days later, I want to assign those individual rows in the table to an authlogic model so the person to whom the record should belong can authenticate to it and make changes. Any code samples, blog posts to better help me understand would be great! Thank You.

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• Advanced Linq query using into

  - by dilbert789

  I have this query that someone else wrote, it's over my head so I'm looking for some direction. What is happening currently is that it's taking numbers where there is a goal and no history entered, or history and no goal, this screws up the calculations as both goal and history for the same item are required on each. The three tables involved are: KPIType Goal KPIHistory What I need: Need all rows from KPIType. Need all goals where there is a matching KPIHistory row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 1 Need all kpiHistory’s where there is a matching Goal row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 2 Current query: var query = from t in dcs.KPIType.Where(k => k.ID <= 23) join g in dcs.Goal.Where(g => g.Dealership.ID == dealershipID && g.YearMonth >= beginDate && g.YearMonth <= endDate ) on t.ID equals g.KPITypeID into results1 join h in dcs.KPIHistory.Where(h => h.Dealership.ID == dealershipID && h.ForDate >= beginDate && h.ForDate <= endDate ) on t.ID equals h.KPIType.ID into results2 orderby t.DisplayOrder select new { t, Goal = results1, KPIHistory = results2 }; query.ToList().ForEach(q => { results.Add(q.t); }); Thanks, I'm happy to answer questions if more info needed.

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• What are some good ways to store performance statistics in a database for querying later?

  - by Nathan

  Goal: Store arbitrary performance statistics of stuff that you care about (how many customers are currently logged on, how many widgets are being processed, etc.) in a database so that you can understand what how your servers are doing over time. Assumptions: A database is already available, and you already know how to gather the information you want and are capable of putting it in the database however you like. Some Ideal Attributes of a Solution Causes no noticeable performance hit on the server being monitored Has a very high precision of measurement Does not store useless or redundant information Is easy to query (lends itself to gathering/displaying useful information) Lends itself to being graphed easily Is accurate Is elegant Primary Questions 1) What is a good design/method/scheme for triggering the storing of statistics? 2) What is a good database design for how to actually store the data? Example answers...that are sort of vague and lame... 1) I could, once per [fixed time interval], store a row of data with all the performance measurements I care about in each column of one big flat table indexed by timestamp and/or server. 2) I could have a daemon monitoring performance stuff I care about, and add a row whenever something changes (instead of at fixed time intervals) to a flat table as in #1. 3) I could trigger either as in #2, but I could store information about each aspect of performance that I'm measuring in separate tables, opening up the possibility of adding tons of rows for often-changing items, and few rows for seldom-changing items. Etc. In the end, I will implement something, even if it's some super-braindead approach I make up myself, but I'm betting there are some really smart people out there willing to share their experiences and bright ideas!

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• Best way to get a single value from a DataTable?

  - by PiersMyers

  I have a number of static classes that contain tables like this: using System; using System.Data; using System.Globalization; public static class TableFoo { private static readonly DataTable ItemTable; static TableFoo() { ItemTable = new DataTable("TableFoo") { Locale = CultureInfo.InvariantCulture }; ItemTable.Columns.Add("Id", typeof(int)); ItemTable.Columns["Id"].Unique = true; ItemTable.Columns.Add("Description", typeof(string)); ItemTable.Columns.Add("Data1", typeof(int)); ItemTable.Columns.Add("Data2", typeof(double)); ItemTable.Rows.Add(0, "Item 1", 1, 1.0); ItemTable.Rows.Add(1, "Item 2", 1, 1.0); ItemTable.Rows.Add(2, "Item 3", 2, 0.75); ItemTable.Rows.Add(3, "Item 4", 4, 0.25); ItemTable.Rows.Add(4, "Item 5", 1, 1.0); } public static DataTable GetItemTable() { return ItemTable; } public static int Data1(int id) { DataRow[] dr = ItemTable.Select("Id = " + id); if (dr.Length == 0) { throw new ArgumentOutOfRangeException("id", "Out of range."); } return (int)dr[0]["Data1"]; } public static double Data2(int id) { DataRow[] dr = ItemTable.Select("Id = " + id); if (dr.Length == 0) { throw new ArgumentOutOfRangeException("id", "Out of range."); } return (double)dr[0]["Data2"]; } } Is there a better way of writing the Data1 or Data2 methods that return a single value from a single row that matches the given id?

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• How to do this Python / MySQL manipulation (match) more efficiently?

  - by NJTechie

  Following is my data : Company Table : ID Company Address City State Zip Phone 1 ABC 123 Oak St Philly PA 17542 7329878901 2 CDE 111 Joe St Newark NJ 08654 3 GHI 211 Foe St Brick NJ 07740 7321178901 4 JAK 777 Wall Ocean NJ 07764 7322278901 5 KLE 87 Ilk St Plains NY 07654 7376578901 6 AB 1 W.House SField PA 87656 7329878901 Branch Office Table : ID Address City State Zip Phone 1 323 Alk St Philly PA 17542 7329832221 1 171 Joe St Newark NJ 08654 3 287 Foe St Brick NJ 07740 7321178901 3 700 Wall Ocean NJ 07764 7322278901 1 89 Blk St Surrey NY 07154 7376222901 File to be Matched (In MySQL): ID Company Address City State Zip Phone 1 ABC 123 Oak St Philly PA 17542 7329878901 2 AB 171 Joe St Newark NJ 08654 3 GHI 211 Foe St Brick NJ 07740 7321178901 4 JAK 777 Wall Ocean NJ 07764 7322278901 5 K 87 Ilk St Plains NY 07654 7376578901 Resulting File : ID Company Address City State Zip Phone appendedID 1 ABC 123 Oak St Philly PA 17542 7329878901 [Original record, field always empty] 1 ABC 171 Joe St Newark NJ 08654 1 [Company Table] 1 ABC 323 Alk St Philly PA 17542 7329832221 1 [Branch Office Table] 1 AB 1 W.House SField PA 87656 7329878901 6 [Partial firm and State, Zip match] 2 CDE 111 Joe St Newark NJ 08654 3 GHI 211 Foe St Brick NJ 07740 7321178901 3 GHI 700 Wall Ocean NJ 07764 7322278901 3 3 GHI 287 Foe St Brick NJ 07740 7321178901 3 4 JAK 777 Wall Ocean NJ 07764 7322278901 5 KLE 87 Ilk St Surrey NY 07654 7376578901 5 KLE 89 Blk St Surrey NY 07154 7376222901 5 Requirement : 1) I have to match each firm on the 'File to be Matched' to that of Company and Branch Office tables (MySQL). 2) If there are multiple exact/partial matches, then the ID from Company, Branch Office table is inserted as a new row in the resulting file. 3) Not all the firms will be matched perfectly, in that case I have to match on partial Company names (like 5/8th of the company name) and any of the address fields and insert them in the resulting file. Please help me out in the most efficient solution for this problem.

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• Linq is returning too many results when joined

  - by KallDrexx

  In my schema I have two database tables. relationships and relationship_memberships. I am attempting to retrieve all the entries from the relationship table that have a specific member in it, thus having to join it with the relationship_memberships table. I have the following method in my business object: public IList<DBMappings.relationships> GetRelationshipsByObjectId(int objId) { var results = from r in _context.Repository<DBMappings.relationships>() join m in _context.Repository<DBMappings.relationship_memberships>() on r.rel_id equals m.rel_id where m.obj_id == objId select r; return results.ToList<DBMappings.relationships>(); } _Context is my generic repository using code based on the code outlined here. The problem is I have 3 records in the relationships table, and 3 records in the memberships table, each membership tied to a different relationship. 2 membership records have an obj_id value of 2 and the other is 3. I am trying to retrieve a list of all relationships related to object #2. When this linq runs, _context.Repository<DBMappings.relationships>() returns the correct 3 records and _context.Repository<DBMappings.relationship_memberships>() returns 3 records. However, when the results.ToList() executes, the resulting list has 2 issues: 1) The resulting list contains 6 records, all of type DBMappings.relationships(). Upon further inspection there are 2 for each real relationship record, both are an exact copy of each other. 2) All relationships are returned, even if m.obj_id == 3, even though objId variable is correctly passed in as 2. Can anyone see what's going on because I've spent 2 days looking at this code and I am unable to understand what is wrong. I have joins in other linq queries that seem to be working great, and my unit tests show that they are still working, so I must be doing something wrong with this. It seems like I need an extra pair of eyes on this one :)

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• If Then Else Statement Condition Being Ignored?

  - by Matma

  I think im going mad but can some show me what im missing, it must be some stupidly simple i just cant see the wood for the trees. BOTH side of this if then else statement are being executed? Ive tried commenting out the true side and moving the condition to a seperate variable with the same result. However if i explicitly set the condition to 1=0 or 1=1 then the if then statement is operating as i would expect. i.e. only executing one side of the equation... The only time ive seen this sort of thing is when the compiler has crashed and is no longer compiling (without visible indication that its not) but ive restarted studio with the same results, ive cleaned the solution, built and rebuilt with no change? please show me the stupid mistake im making using vs2005 if it matters. Dim dset As DataSet = New DataSet If (CboCustomers.SelectedValue IsNot Nothing) AndAlso (CboCustomers.SelectedValue <> "") Then Dim Sql As String = "Select sal.SalesOrderNo As SalesOrder,cus.CustomerName,has.SerialNo, convert(varchar,sal.Dateofpurchase,103) as Date from [dbo].[Customer_Table] as cus " & _ " inner join [dbo].[Hasp_table] as has on has.CustomerID=cus.CustomerTag " & _ " inner join [dbo].[salesorder_table] as sal On sal.Hasp_ID =has.Hasp_ID Where cus.CustomerTag = '" & CboCustomers.SelectedValue.ToString & "'" Dim dap As SqlDataAdapter = New SqlDataAdapter(Sql, FormConnection) dap.Fill(dset, "dbo.Customer_Table") DGCustomer.DataSource = dset.Tables("dbo.Customer_Table") Else Dim erm As String = "wtf" End If

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• How to create refresh statements for TableAdapter objects in Visual Studio?

  - by Mark Wilkins

  I am working on developing an ADO.NET data provider and an associated DDEX provider. I am unable to convince the Visual Studio TableAdapater Configuration Wizard to generate SQL statements to refresh the data table after inserts and updates. It generates the insert and delete statements but will not produce the select statements to do the refresh. The functionality referred to can be accessed by dropping a table from the Server Explorer (inside Visual Studio) onto a DataSet (e.g., DataSet1.xsd). It creates a TableAdapter object and configures SELECT, UPDATE, DELETE, and INSERT statements. If you right click on the TableAdapter object, the context menu has a “Configure” option that starts the “TableAdapter Configuration Wizard”. The first dialog of that wizard has an Advanced Options button, which leads to an option titled “Refresh the data table”. When used with SQL Server tables, that option causes a statement of the form “select field1, field2, …” to be added on to the end of the commands for the TableAdapter’s InsertCommand and UpdateCommand. Do you have any idea what type property or interface might need to be exposed from the DDEX provider (or maybe the ADO.NET data provider) in order to make Visual Studio add those refresh statements to the update/insert commands? The MSDN documentation for the Advanced SQL Generation Options Dialog Box has a note stating, “Refreshing the data table is only supported on databases that support batching of SQL statements.” This seems to imply that a .NET data provider might need to expose some property indicating such behavior is supported. But I cannot find it. Any ideas?

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• binding nested json object value to a form field

  - by Jack

  I am building a dynamic form to edit data in a json object. First, if something like this exists let me know. I would rather not build it but I have searched many times for a tool and have found only tree like structures that require entering quotes. I would be happy to treat all values as strings. This edit functionality is for end users so it needs to be easy an not intimidating. So far I have code that generates nested tables to represent a json object. For each value I display a form field. I would like to bind the form field to the associated nested json value. If I could store a reference to the json value I would build an array of references to each value in a json object tree. I have not found a way to do that with javascript. My last resort approach will be to traverse the table after edits are made. I would rather have dynamic updates but a single submit would be better than nothing. Any ideas? // the json in files nests only a few levels. Here is the format of a simple case, { "researcherid_id":{ "id_key":"researcherid_id", "description":"Use to retrieve bibliometric data", "url_template" :[ { "name": "Author Detail", "url": "http://www.researcherid.com/rid/${key}" } ] } } $.get('file.json',make_json_form); function make_json_form(response) { dataset = $.secureEvalJSON(response); // iterate through the object and generate form field for string values. } // Then after the form is edited I want to display the raw updated json (then I want to save it but that is for another thread) // now I iterate through the form and construct the json object // I would rather have the dataset object var updated on focus out after each edit. function show_json(form_id){ var r = {}; var el = document.getElementById(form_id); table_to_json(r,el,null); $('body').html(formattedJSON(r)); }

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• Extract primary key from MySQL in PHP

  - by Parth

  I have created a PHP script and I am lacking to extract the primary key, I have given flow below, please help me in how can i modify to get primary key I am using MySQL DB, working for Joomla, My requirement is tracking the activity like insert/update/delete on any table and store it in another audit table using triggers, i.e. I am doing Auditing. DB's table structure: Few tables dont have any PK nor auto increment key Flow of my script is : I fetch out all table from DB. I check whether the table have any trigger or not. If yes then it moves to check nfor next table and so on. If it does'nt find any trigger then it creates the triggers for the table, such that, -it first checks if the table has any primary key or not(for inserting in Tracking audit table for every change made) if it has the primary key then it uses it further in creation of trigger. if it doesnt find any PK then it proceeds further in creating the trigger without inserting any id in audit table Now here, My problem is I need the PK every time so that I can record the id of any particular table in which the insert/update/delete is performed, so that further i can use this audit track table to replicate in production DB.. Now as I haave mentioned earlier that I am not available with PK/auto-incremented in some table, then what should I do get the particular id in which change is done? please guide me...GEEKS!!!

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• Why are my Fluent NHibernate SubClass Mappings generating redundant columns?

  - by Brook

  I'm using Fluent NHibernate 1.x build 694, built against NH 3.0 I have the following entities public abstract class Card { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual string Description { get; set; } public virtual Product Product { get; set; } public virtual Sprint Sprint { get; set; } } public class Story:Card { public virtual double Points { get; set; } public virtual int Priority { get; set; } public virtual IList<Task> Tasks { get; set; } } And the following mappings public class CardMap:ClassMap<Card> { public CardMap() { Id(c => c.Id) .Index("Card_Id"); Map(c => c.Name) .Length(50) .Not.Nullable(); Map(c => c.Description) .Length(1024) .Not.Nullable(); References(c=>c.Product) .Not.Nullable(); References(c=>c.Sprint) .Nullable(); } } public class StoryMap : SubclassMap<Story> { public StoryMap() { Map(s => s.Points); Map(s => s.Priority); HasMany(s => s.Tasks); } } When I generate my Schema, the tables are created as follows Card --------- Id Name Description Product_id Sprint_id Story ------------ Card_id Points Priority Product_id Sprint_id What I would have expected would have been to see the columns Product_id and Sprint_id ONLY in the Card table, not the Story table. What am I doing wrong or misunderstanding?

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• Entity Framework. Updating EntityCollection using disconnected objects via navigation property.

  - by yougotiger

  I have a question, much liket this unanswered one. I'm trying to work with the entity framework, and having a tough time getting my foreign tables to update. I have something basically like this in the DB: Incident (table): -ID -other fields Responses (table): -FK:Incident.ID -other fields And and entities that match: Incident (entity) -ID -Other fields -Responses (EntityCollection of Responses via navigation property) Each Incident can have 0 or more responses. In my Webpage, I have a form to allow the user to enter all the details of an Incident, including a list of responses. I can add everything to the database when a new Incident is created, however I'm having difficulty with editing the Incident. When the page loads for edit, I populate the form and then store the responses in the viewstate. When the user changes the list of responses (adds one, deletes one or edits one). I store this back into the viewstate. Then when the user clicks the save button, I'd like to save the changes to the Incident and the Responses back to the DB. I cannot figure out how to get the responses from the detached viewstate into the Incident object so that they can be updated together. Currently when the user clicks save, I'm getting the Incident to edit from the db, making changes to the Incident's fields and then saving it back to the DB. However I can't figure out how to have the detached list of responses from the viewstate attach to the Incident. I have tried the following without success: Clearning the Incident.Responses collection and adding the ones from the viewstate back in: Incident.Responses.Clear() for each objResponse in Viewstate("Responses") Incident.Responses.add(objResponse) next Creating an EntityCollection from my list and then assiging that to the Incident.Responses Incident.Responses = EntityCollectionFromViewstateList Iterating through the responses in Incident.Response and assigning the corresponding object from viewstate: for each ObjResponse in Incident.Responses objResponse = objCorrespondingModifedResonseFromViewState Next These all fail, I'd like to be able to merge the changes into the Inicdent object so that when the BLL calls SaveChanges on the changes to both the Incident and Responses will happen at the same time. Any suggestions? I keep finding lots of stuff about assigning foreign keys (singular), but I haven't found a great solution for doing a set of entities assigned to another entity in this manner.

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• Using Partitions for a large MySQL table

  - by user293594

  An update on my attempts to implement a 505,000,000-row table on MySQL on my MacBook Pro: Following the advice given, I have partitioned my table, tr: i UNSIGNED INT NOT NULL, j UNSIGNED INT NOT NULL, A FLOAT(12,8) NOT NULL, nu BIGINT NOT NULL, KEY (nu), key (A) with a range on nu. nu ought to be a real number, but because I only have 6-d.p. accuracy and the maximum value of nu is 30000. I multiplied it by 10^8 made it a BIGINT - I gather one can't use FLOAT or DOUBLE values to PARTITION a MySQL table. Anyway, I have 15 partitions (p0: nu<25,000,000,000, p1: nu<50,000,000,000, etc.). I was thinking that this should speed up a typical to SELECT: SELECT * FROM tr WHERE nu>95000000000 AND nu<100000000000 AND A.>1. to something of the order of the same query on a table consisting of only the data in the relevant partition (<30 secs). But it's taking 30mins+ to return rows for queries within a partition and double that if the query is for rows spanning two (contiguous) partitions. I realise I could just have 15 different tables, and query them separately, but is there a way to do this 'automatically' with partitions? Has anyone got any suggestions?

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• Method for defining simultaneous has-many and has-one associations between two models in CakePHP?

  - by Hobonium

  One thing with which I have long had problems, within the CakePHP framework, is defining simultaneous hasOne and hasMany relationships between two models. For example: BlogEntry hasMany Comment BlogEntry hasOne MostRecentComment (where MostRecentComment is the Comment with the most recent created field) Defining these relationships in the BlogEntry model properties is problematic. CakePHP's ORM implements a has-one relationship as an INNER JOIN, so as soon as there is more than one Comment, BlogEntry::find('all') calls return multiple results per BlogEntry. I've worked around these situations in the past in a few ways: Using a model callback (or, sometimes, even in the controller or view!), I've simulated a MostRecentComment with: $this->data['MostRecentComment'] = $this->data['Comment'][0]; This gets ugly fast if, say, I need to order the Comments any way other than by Comment.created. It also doesn't Cake's in-built pagination features to sort by MostRecentComment fields (e.g. sort BlogEntry results reverse-chronologically by MostRecentComment.created. Maintaining an additional foreign key, BlogEntry.most_recent_comment_id. This is annoying to maintain, and breaks Cake's ORM: the implication is BlogEntry belongsTo MostRecentComment. It works, but just looks...wrong. These solutions left much to be desired, so I sat down with this problem the other day, and worked on a better solution. I've posted my eventual solution below, but I'd be thrilled (and maybe just a little mortified) to discover there is some mind-blowingly simple solution that has escaped me this whole time. Or any other solution that meets my criteria: it must be able to sort by MostRecentComment fields at the Model::find level (ie. not just a massage of the results); it shouldn't require additional fields in the comments or blog_entries tables; it should respect the 'spirit' of the CakePHP ORM. (I'm also not sure the title of this question is as concise/informative as it could be.)

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• Using nohup mysqldump from php script is inserting a '!' and breaking to a new line.

  - by Aglystas

  I'm trying to run a mysqldump from php using the nohup command to prevent the script from hanging. Here's the command (The database is mc6_erik_test, everything else is just a table list until you get to the end) exec("mysqldump -u root -pPassword -h vfmy1-dev.mountainmedia.com mc6_erik_test access_log admin affiliate affiliate_2_product authorized_ip category category_2_product claim_code claim_code_log country_exclude customer customer_2_subscription customer_account_log customer_address customer_bill customer_discount customer_ip customer_key email_bulk_log email_draft email_queue email_queue_log email_template endicia_log gift_wrap image_bulk_upload log mailing_list manufacturer merchant merchant_checkout merchant_ip merchant_ship merchant_ship_conf new_account_temp order_dest order_item order_item_2_dest order_item_2_package order_item_log order_item_registrant order_note order_package order_package_label orders package package_2_product pref product product_2_supplier product_also product_event_date product_image product_option product_related product_review product_review_helpful product_ship_disable report search_log subscription supplier temp_product transaction_account transactions wish_list wish_list_fill wish_list_item --opt --where='merchant_id=\'6\'' /tmp/sync_db_card_20100519105358.sql"); As you can see it's really long, because I have to specifically include only the tables I want to dump. The command works great from the command line, however when I run it through a web script towards the end the following is being used as the command... supplier temp_product transaction_account transactio! ns wish_list wish_list_fill wish_list_item --opt --where='merchant_id="6"' > /tmp/sync_db_card_20100519105358.sql So the table 'transactions' is being split by an exclamation point and newline. The rest of the command is exactly the same. And if I run this through the php-cli interface it doesn't happen only when I try running it via the webserver using nohup. I'm wondering if there is some inherit string length to using the exec command within a php script, or really if anyone has any general idea what is going on here.

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• Foreign key not working in MySQL: Why can I INSERT a value that's not in the foreign column?

  - by stalepretzel

  I've created a table in MySQL: CREATE TABLE actions ( A_id int NOT NULL AUTO_INCREMENT, type ENUM('rate','report','submit','edit','delete') NOT NULL, Q_id int NOT NULL, U_id int NOT NULL, date DATE NOT NULL, time TIME NOT NULL, rate tinyint(1), PRIMARY KEY (A_id), CONSTRAINT fk_Question FOREIGN KEY (Q_id) REFERENCES questions(P_id), CONSTRAINT fk_User FOREIGN KEY (U_id) REFERENCES users(P_id)); This created the table I wanted just fine (although a "DESCRIBE actions;" command showed me that the foreign keys were keys of type MUL, and I'm not sure what this means). However, when I try to enter a Q_id or a U_id that does not exist in the questions or users tables, MySQL still allows these values. What did I do wrong? How can I prevent a table with a foreign key from accepting invalid data? If I add TYPE=InnoDB to the end, I get an error: ERROR 1005 (HY000): Can't create table './quotes/actions.frm' (errno: 150) Why might that happen? I'm told that it's important to enforce data integrity with functional foreign keys, but also that InnoDB should not be used with MySQL. What do you recommend?

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• Creating an SQL variable character column > 255 characters supporting multiple databases

  - by Piers

  I have an application that stores data through an ODBC data source of the user's choosing. So far it has worked well on a range of database systems (e.g. JET, Oracle, SQL Server), as the SQL syntax is fairly simple. Now I am running into a problem where I need to store more than 255 characters in my strings. Previously I created the table using column type VARCHAR (255). Now if I try to create a table using, e.g. VARCHAR (512) then it falls over on Access databases. I know that I can use the MEMO type for Access, but this is non-standard SQL and will thus likely fail on other database systems (e.g. Oracle). Is there any widely supported SQL standard for creating text columns wider than 255 characters, or do I need to find another solution? The alternatives seem to me to be: 1) Profile the database system and customise the SQL CREATE TABLE command based on the database system. I don't like this as it defeats the purpose of using ODBC. 2) Add extra columns of 255 chars as required (e.g. LONGSTRING1, LONGSTRING2, ...) and concatenate after reading. I don't like this because it means the number of columns can vary between tables and it complicates read/write. Are there any other viable alternatives to these two options? Or is it possible to have an SQL compliant CREATE TABLE command supported by the majority of database vendors, that supports strings longer than 255 chars?

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• SQL Design: representing a default value with overrides?

  - by Mark Harrison

  I need a sparse table which contains a set of "override" values for another table. I also need to specify the default value for the items overridden. For example, if the default value is 17, then foo,bar,baz will have the values 17,21,17: table "things" table "xvalue" name stuff name xval ---- ----- ---- ---- foo ... bar 21 bar ... baz ... If I don't care about a FK from xvalue.name - things.name, I could simply put a "DEFAULT" name: table "xvalue" name xval ---- ---- DEFAULT 17 bar 21 But I like having a FK. I could have a separate default table, but it seems odd to have 2x the number of tables. table "xvalue_default" xval ---- 17 table "xvalue" name xval ---- ---- bar 21 I could have a "defaults table" tablename attributename defaultvalue xvalue xval 17 but then I run into type issues on defaultvalue. My operations guys prefer as compact a representation as possible, so they can most easily see the "diff" or deviations from the default. What's the best way to represent this, including the default value? This will be for Oracle 10.2 if that makes a difference.

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• Is it possible to group records belonging to an entity in dbunit?

  - by Joshua

  Our JPA entity model auto-generates primary key identifiers for user, user_address tables. Would it be possible to group these entities given below via dbunit, so that I don't need to provide neither the primary key as well as the foreign key reference from user_address.user_id. It is getting very hard to maintain these keys (i.e. I would prefer to group the primary record 'user' and the child records 'user_address' so that dbunit can group them automatically by looking up the entity metadata). Is it achievable? <user id="1" first_name="Josh" creation_date="2009-07-11 15:45:28"/> <user_address id="1" user_id="1" address="Main St" city="Los Angeles"/> I would prefer something like this <!-- First user --> <user first_name="Josh" creation_date="2009-07-11 15:45:28"/> <user_address address="Main St" city="Los Angeles"/> <!-- Second user --> <user first_name="Mary" creation_date="2009-07-11 15:45:28"/> <user_address address="Taylors St" city="San Jose"/>

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• PostgreSQL, Foreign Keys, Insert speed & Django

  - by Miles

  A few days ago, I ran into an unexpected performance problem with a pretty standard Django setup. For an upcoming feature, we have to regenerate a table hourly, containing about 100k rows of data, 9M on the disk, 10M indexes according to pgAdmin. The problem is that inserting them by whatever method literally takes ages, up to 3 minutes of 100% disk busy time. That's not something you want on a production site. It doesn't matter if the inserts were in a transaction, issued via plain insert, multi-row insert, COPY FROM or even INSERT INTO t1 SELECT * FROM t2. After noticing this isn't Django's fault, I followed a trial and error route, and hey, the problem disappeared after dropping all foreign keys! Instead of 3 minutes, the INSERT INTO SELECT FROM took less than a second to execute, which isn't too surprising for a table <= 20M on the disk. What is weird is that PostgreSQL manages to slow down inserts by 180x just by using 3 foreign keys. Oh, disk activity was pure writing, as everything is cached in RAM; only writes go to the disks. It looks like PostgreSQL is working very hard to touch every row in the referred tables, as 3MB/sec * 180s is way more data than the 20MB this new table takes on disk. No WAL for the 180s case, I was testing in psql directly, in Django, add ~50% overhead for WAL logging. Tried @commit_on_success, same slowness, I had even implemented multi row insert and COPY FROM with psycopg2. That's another weird thing, how can 10M worth of inserts generate 10x 16M log segments? Table layout: id serial primary, a bunch of int32, 3 foreign keys to small table, 198 rows, 16k on disk large table, 1.2M rows, 59 data + 89 index MB on disk large table, 2.2M rows, 198 + 210MB So, am I doomed to either drop the foreign keys manually or use the table in a very un-Django way by defining saving bla_id x3 and skip using models.ForeignKey? I'd love to hear about some magical antidote / pg setting to fix this.

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• Database nesting layout confusion

  - by arzon

  I'm no expert in databases and a beginner in Rails, so here goes something which kinda confuses me... Assuming I have three classes as a sample (note that no effort has been made to address any possible Rails reserved words issue in the sample). class File < ActiveRecord::Base has_many :records, :dependent => :destroy accepts_nested_attributes_for :records, :allow_destroy => true end class Record < ActiveRecord::Base belongs_to :file has_many :users, :dependent => :destroy accepts_nested_attributes_for :users, :allow_destroy => true end class User < ActiveRecord::Base belongs_to :record end Upon entering records, the database contents will appear as such. My issue is that if there are a lot of Files for the same Record, there will be duplicate record names. This will also be true if there will be multiple Records for the same user in the the Users table. I was wondering if there is a better way than this so as to have one or more files point to a single Record entry and one or more Records will point to a single User. BTW, the File names are unique. Files table: id name 1 name1 2 name2 3 name3 4 name4 Records table: id file_id record_name record_type 1 1 ForDaisy1 ... 2 2 ForDonald1 ... 3 3 ForDonald2 ... 4 4 ForDaisy1 ... Users table: id record_id username 1 1 Daisy 2 2 Donald 3 3 Donald 4 4 Daisy Is there any way to optimize the database to prevent duplication of entries, or this should really the correct and proper behavior. I spread out the database into different tables to be able to easily add new columns in the future.

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• User preferences using SQL and JavaScript

  - by Shyam

  Hi, I am using Server Side JavaScript - yes, I am actually using Server Side JavaScript. To complexify things even more, I use Oracle as a backend database (10g). With some crazy XSLT and mutant-like HTML generation, I can build really fancy web forms - yes, I am aware of Rails and other likewise frameworks and I choose the path of horror instead. I have no JQuery or other fancy framework at my disposal, just plain ol' JavaScript that should be supported by the underlying engine called Mozilla Rhino. Yes, it is insane and I love it. So, I have a bunch of tables at my disposal and some of them are filled with associative keys that link to values. As I am a people pleaser, I want to add some nifty user-preference driven solutions. My users have all an unique user_id and this user_id is available during the entire session. My initial idea is to have a user preference table, where I have "three" columns: user_id, feature and pref_string. Using a delimiter, such as : or - (haven't thought about a suitable one yet), I could like store a bunch of preferences as a list and store its elements inside an array using the .split-method (similar like the PHP-explode function). The feature column could be like the table name or some identifier for the "feature" i want to link preferences too. I hate hardcoding objects, especially as I want to be able to back these up and reuse this functionality application-wide. Of course I would love better ideas, just keep in mind I cannot just add a library that easily. These preferences could be like "joined" to the table, so I can query it and use its values. I hope it doesn't sounds too complex, because well.. its basically something really simple I need. Thanks!

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• Select multiple records from sql database table in a master-detail scenario

  - by Trex

  Hello, I have two tables in a master-detail relationship. The structure is more or less as follows: Master table: MasterID, DetailID, date, ... masterID1, detailID1, 2010/5/1, .... masterID2, detailID1, 2008/6/14, ... masterID3, detailID1, 2009/5/25, ... masterID4, detailID2, 2008/7/24, ... masterID5, detailID2, 2010/4/1, ... masterID6, detailID4, 2008/9/16, ... Details table: DetailID, ... detailID1, ... detailID2, ... detailID3, ... detailID4, ... I need to get all the records from the details table plus the LAST record from the master table (last by the date in the master table). Like this: detailID1, masterID1, 2010/5/1, .... detailID2, masterID5, 2010/4/1, ... detailID3, null, null, ... detailID4, masterID6, 2008/9/16, ... I have no idea how to do this. Can anybody help me? Thanks a lot. Jan

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• Trying to insert a row using stored procedured with a parameter binded to an expression.

  - by Arvind Singh

  Environment: asp.net 3.5 (C# and VB) , Ms-sql server 2005 express Tables Table:tableUser ID (primary key) username Table:userSchedule ID (primary key) thecreator (foreign key = tableUser.ID) other fields I have created a procedure that accepts a parameter username and gets the userid and inserts a row in Table:userSchedule Problem: Using stored procedure with datalist control to only fetch data from the database by passing the current username using statement below works fine protected void SqlDataSourceGetUserID_Selecting(object sender, SqlDataSourceSelectingEventArgs e) { e.Command.Parameters["@CurrentUserName"].Value = Context.User.Identity.Name; } But while inserting using DetailsView it shows error Procedure or function OASNewSchedule has too many arguments specified. I did use protected void SqlDataSourceCreateNewSchedule_Selecting(object sender, SqlDataSourceSelectingEventArgs e) { e.Command.Parameters["@CreatedBy"].Value = Context.User.Identity.Name; } DetailsView properties: autogen fields: off, default mode: insert, it shows all the fields that may not be expected by the procedure like ID (primary key) not required in procedure and CreatedBy (user id ) field . So I tried removing the 2 fields from detailsview and shows error Cannot insert the value NULL into column 'CreatedBy', table 'D:\OAS\OAS\APP_DATA\ASPNETDB.MDF.dbo.OASTest'; column does not allow nulls. INSERT fails. The statement has been terminated. For some reason parameters value is not being set. Can anybody bother to understand this and help?

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