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  • Returning IEnumerable<T> vs IQueryable<T>

    - by stackoverflowuser
    what is the difference between returning iqueryable vs ienumerable. IQueryable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; IEnumerable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; Will both be deferred execution? When should one be preferred over the other?

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  • How Can I Generate Random Unqiue Numbers in C#

    - by peace
    public int GenPurchaseOrderNum() { Random random = new Random(); _uniqueNum = random.Next(13287, 21439); return UniqueNum; } I removed unique constraint from the PONumber column in the db because an employee should only generate P.O. # when the deal is set. Otherwise, P.O. # would have 0. P.O. Number used to have unique constraint, this forces employee to generate P.O. in all cases so the db doesn't throw unique constraint error. Since i removed the unique constraint, any quote doesn't have P.O. will carry 0 value. Otherwise, a unique value is generated for P.O. #. However, i don't have a unique constraint in db which makes it hard for me to know whether the application generated P.O. # is unique or not. What should i do? I hope my question is clear enough

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  • Using subselect to accomplish LEFT JOIN

    - by Andre
    Is is possible to accomplish the equivalent of a LEFT JOIN with subselect where multiple columns are required. Here's what I mean. SELECT m.*, (SELECT * FROM model WHERE id = m.id LIMIT 1) AS models FROM make m As it stands now doing this gives me a 'Operand should contain 1 column(s)' error. Yes I know this is possible with LEFT JOIN, but I was told it was possible with subselect to I'm curious as to how it's done.

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  • Computed column should result to string

    - by strakastroukas
    Here is a snap of my database. Both col1 and col2 are declared as int. My ComputedColumn currently adds the Columns 1 and 2, as follows... col1 col2 ComputedColumn 1 2 3 4 1 5 Instead of this, my ComputedColumn should join the columns 1 and 2 (includimg the '-' character in the middle) as follows... col1 col2 ComputedColumn 1 2 1-2 4 1 4-1 So, what is the correct syntax?

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  • How to Update the primary key of table which is referenced as foreign key in another table?

    - by Mobin
    Suppose a Table "Person" having columns "SSN","Name","Address" and another Table "Contacts" having "Contact_ID","Contact_Type","SSN"(primary key of Person) similarly Table "Records" having "Record_ID","Record_Type","SSN"(primary key of Person) Now i want that when i change or update SSN in person table that accordingly changes in other 2 tables. If anyone can help me with a trigger for that Or how to pass foreign key constraints for tables

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  • How transform this find_by_sql to named_scope?

    - by keruilin
    How can I possibly turn into named_scope? def self.hero_badge_awardees return User.find_by_sql("select users.*, awards.*, badges.badge_type from users, awards, badges where awards.user_id = users.id and badges.id = awards.badge_id and badges.badge_type = 'HeroBadge'") end

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  • TSQL: grouping customer orders by week

    - by fishhead
    I have a table with a collection of orders. The fields are: customerName (text) DateOfOrder (datetime). I would like to show totals of orders per week per customer. I would like to have it arranged for the Friday of each week so that it looks like this: all dates follow mm/dd/yyyy "bobs pizza", 3/5/2010, 10 "the phone co",3/5/2010,5 "bobs pizza", 3/12/2010, 3 "the phone co",3/12/2010,11 Could somebody please show me how to do this? Thanks

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  • Why index_merge is not used here using MySQL?

    - by user198729
    Setup: mysql> create table t(a integer unsigned,b integer unsigned); mysql> insert into t(a,b) values (1,2),(1,3),(2,4); mysql> create index i_t_a on t(a); mysql> create index i_t_b on t(b); mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 3 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Is there something I'm missing? Update mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 1863 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Version: mysql> select version(); +----------------------+ | version() | +----------------------+ | 5.1.36-community-log | +----------------------+

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  • Deeply nested subqueries for traversing trees in MySQL

    - by nickf
    I have a table in my database where I store a tree structure using the hybrid Nested Set (MPTT) model (the one which has lft and rght values) and the Adjacency List model (storing parent_id on each node). my_table (id, parent_id, lft, rght, alias) This question doesn't relate to any of the MPTT aspects of the tree but I thought I'd leave it in in case anyone had a good idea about how to leverage that. I want to convert a path of aliases to a specific node. For example: "users.admins.nickf" would find the node with alias "nickf" which is a child of one with alias "admins" which is a child of "users" which is at the root. There is a unique index on (parent_id, alias). I started out by writing the function so it would split the path to its parts, then query the database one by one: SELECT `id` FROM `my_table` WHERE `parent_id` IS NULL AND `alias` = 'users';-- 1 SELECT `id` FROM `my_table` WHERE `parent_id` = 1 AND `alias` = 'admins'; -- 8 SELECT `id` FROM `my_table` WHERE `parent_id` = 8 AND `alias` = 'nickf'; -- 37 But then I realised I could do it with a single query, using a variable amount of nesting: SELECT `id` FROM `my_table` WHERE `parent_id` = ( SELECT `id` FROM `my_table` WHERE `parent_id` = ( SELECT `id` FROM `my_table` WHERE `parent_id` IS NULL AND `alias` = 'users' ) AND `alias` = 'admins' ) AND `alias` = 'nickf'; Since the number of sub-queries is dependent on the number of steps in the path, am I going to run into issues with having too many subqueries? (If there even is such a thing) Are there any better/smarter ways to perform this query?

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  • Entity Framework Duplicate type name within an assembly (6.1.0)

    - by CodeMilian
    I am not sure what is going on but I keep getting the following exception when doing a query. "Duplicate type name within an assembly." I have not been able to find a solution on the web. I had resolved the issue by removing entity framework from all the projects in the solutions and re-installing using nugget. Then all of the sudden the exception is back. I have verified my table schema over and over and find nothing wrong with. This is the query causing the exception. var BaseQuery = from Users in db.Users join UserInstalls in db.UserTenantInstalls on Users.ID equals UserInstalls.UserID join Installs in db.TenantInstalls on UserInstalls.TenantInstallID equals Installs.ID where Users.Username == Username && Users.Password == Password && Installs.Name == Install select Users; var Query = BaseQuery.Include("UserTenantInstalls.TenantInstall"); return Query.FirstOrDefault(); As I mentioned previously the same query was working before. The data has not changed and the code has not changed.

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  • Zend_Db_Select: regrouping conditions in where clause

    - by pvledoux
    Hi, I would like to do something like this: $select = $myTbl->select() ->from('download_log') ->joinLeft(...... etc........ ->joinLeft(...... etc........ ->joinLeft(...... etc........); //Filter all configured bots (Google, Yahoo, etc.) if(isset($this->_config->statistics->bots)){ $bots = explode(',',$this->_config->statistics->bots); foreach ($bots as $bot){ $select = $select->orWhere("user_agent NOT LIKE '%$bot%'"); } } $select = $select->where("download_log.download_log_ts BETWEEN '".$start_date." 00:00:00' AND '".$end_date." 23:59:59'"); But the outputed query is not correct because of the orWhere clauses are not grouped together in a unique AND clause. I would like to know if it is possible to regrouped those OR clauses in a pair of parentheres. My current alternative is the following: //Filter all configured bots (Google, Yahoo, etc.) if(isset($this->_config->statistics->bots)){ $bots = explode(',',$this->_config->statistics->bots); foreach ($bots as $bot){ $stmt .= "user_agent NOT LIKE '%$bot%' OR "; } $stmt = substr($stmt,0,strlen($stmt)-3); //remove the last OR $select = $select->where("($stmt)"); } Thanks!

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  • database setup for web application

    - by vbNewbie
    I have an application that requires a database and I have already setup tables but not sure if they match the requirements of the app. The app is a crawler which fetches web urls, crawls and stores appropriate urls and posts and all this is based on client requests which are stored as projects. So for each url stored there is one post and for client there are many projects and for each project there are many types of requests. So we get a client with a request and assign them a project name and then use the request to search for content and store the url and post. A request could already exist and should not be duplicated but should be associated with the right client and project and post etc. Here is my schema now: url table: urlId PK queryId FK url post table: postId PK urlId FK post date request table: queryId PK request client table: clientId PK client Name projectId FK project table: projectID PK queryID FK project Does this look right? or does anyone have suggestions. Of course my stored procedures and insert statements will have to be in depth.

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  • LINQ Query returns nothing.

    - by gtas
    Why is this query returns 0 lines? There is a record matching the arguments. Deafkaw.Where(p => (p.ImerominiaKataxorisis >= aDate && p.ImerominiaKataxorisis <= DateTime.Now) && (p.Year == etos && p.IsYpodeigma == false) ).ToList(); Am i missing something?

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  • A table that has relation to itself issue

    - by Mostafa
    Hi , I've defined table with this schema : CREATE TABLE [dbo].[Codings]( [Id] [int] IDENTITY(1,1) NOT NULL, [ParentId] [int] NULL, [CodeId] [int] NOT NULL, [Title] [nvarchar](50) COLLATE Arabic_CI_AI NOT NULL, CONSTRAINT [PK_Codings] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] And fill it up with data like this : Id ParentId CodeId Title ----------- ----------- ----------- ---------- 1 NULL 0 Gender 2 1 1 Male 3 1 2 Female 4 NULL 0 Educational Level 5 4 1 BS 6 4 2 MS 7 4 3 PHD Now , I'm looking for a solution , in order , When i delete a record that is parent ( like Id= 1 or 4 ), It delete all child automatically ( all records that their ParentId is 1 or 4 ) . I supposed i can do it via relation between Id and Parent Id ( and set cascade for delete rule ) , But when i do that in MMS , the Delete Rule or Update Rule in Properties is disabled . My question is , What can i do to accomplish this ? Thank you

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  • Avoiding Nested Queries

    - by Midhat
    How Important is it to avoid nested queries. I have always learnt to avoid them like a plague. But they are the most natural thing to me. When I am designing a query, the first thing I write is a nested query. Then I convert it to joins, which sometimes takes a lot of time to get right. And rarely gives a big performance improvement (sometimes it does) So are they really so bad. Is there a way to use nested queries without temp tables and filesort

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  • MySQL database query returns empty result

    - by user1791096
    I am doing a data migration and getting empty result of simple query with one join. Following is the query Select * from users u INNER JOIN temp_users tu ON tu.uid = u.uid There hundreds of records which have same uid in both tables, but this query returns only one record. Following is the structure of tables users table uid: varchar(50) utf8_general_ci Yes NULL temp_users table uid: varchar(50) utf8_general_ci Yes NULL Is there anyone who faced same problem?

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  • Using CASE Statements in LEFT OUTER JOIN in SQL

    - by s khan
    I've got a scenario where I want to switch on two different tables in an outer join. It goes something like this:- select mytable.id, yourtable.id from mytable left outer join (case when mytable.id = 2 then table2 yourtable on table1.id = table2.id else table3 yourtable on table1.id = table3.id end) ...but it doesn't work. Any suggestions?

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  • SQLserver multithreaded locking with TABLOCKX

    - by WilfriedVS
    I have a table "tbluser" with 2 fields: userid = integer (autoincrement) user = nvarchar(100) I have a multithreaded/multi server application that uses this table. I want to accomplish the following: Guarantee that field user is unique in my table Guarantee that combination userid/user is unique in each server's memory I have the following stored procedure: CREATE PROCEDURE uniqueuser @user nvarchar(100) AS BEGIN BEGIN TRAN DECLARE @userID int SET nocount ON SET @userID = (SELECT @userID FROM tbluser WITH (TABLOCKX) WHERE [user] = @user) IF @userID <> '' BEGIN SELECT userID = @userID END ELSE BEGIN INSERT INTO tbluser([user]) VALUES (@user) SELECT userID = SCOPE_IDENTITY() END COMMIT TRAN END Basically the application calls the stored procedure and provides a username as parameter. The stored procedure either gets the userid or insert the user if it is a new user. Am I correct to assume that the table is locked (only one server can insert/query)?

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  • Arrays in database tables and normalization

    - by Ivan Petrov
    Hi! Is it smart to keep arrays in table columns? More precisely I am thinking of the following schema which to my understanding violates normalization: create table Permissions( GroupID int not null default(-1), CategoryID int not null default(-1), Permissions varchar(max) not null default(''), constraint PK_GroupCategory primary key clustered(GroupID,CategoryID) ); and this: create table Permissions( GroupID int not null default(-1), CategoryID int not null default(-1), PermissionID int not null default(-1), constraint PK_GroupCategory primary key clustered(GroupID,CategoryID) ); UPD: Forgot to mention, in the scope of this concrete question we will consider that the "fetch rows that have permission X" won't be performed, instead all the lookups will be made by GroupID and CategoryID only Thoughts? Thanks in advance!

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  • Bulk inserting and updating with Entity Framework (Probably a better alternative?)

    - by Dave
    I have a data set of devices, addresses, and companies that I need to import into our database, with the catch that our database may already include a specific device/address/company that is included in the new data set. If that is the case, I need to update that entry with the new information in the data set, excluding addresses. We check if an exact copy of that address exists, otherwise we make a new entry. My issue is that it is very slow to attempt to grab a device/company in EF and if it exist updated it, otherwise insert it. To fix this I tried to get all the companies, devices, and addresses and insert them into respective hashmaps, and check if the identifier of the new data exists in the hashmap. This hasn't led to any performance increases. I've included my code below. Typically I would do a batch insert, I'm not sure what I would do for a batch update though. Can someone advise a different route? var context = ObjectContextHelper.CurrentObjectContext; var oldDevices = context.Devices; var companies = context.Companies; var addresses = context.Addresses; Dictionary<string, Company> companyMap = new Dictionary<string, Company>(StringComparer.OrdinalIgnoreCase); Dictionary<string, Device> deviceMap = new Dictionary<string, Device>(StringComparer.OrdinalIgnoreCase); Dictionary<string, Address> addressMap = new Dictionary<string, Address>(StringComparer.OrdinalIgnoreCase); foreach (Company c in companies) { if (c.CompanyAccountID != null && !companyMap.ContainsKey(c.CompanyAccountID)) companyMap.Add(c.CompanyAccountID, c); } foreach (Device d in oldDevices) { if (d.SerialNumber != null && !deviceMap.ContainsKey(d.SerialNumber)) deviceMap.Add(d.SerialNumber, d); } foreach (Address a in addresses) { string identifier = GetAddressIdentifier(a); if (!addressMap.ContainsKey(identifier)) addressMap.Add(identifier, a); } foreach (DeviceData.TabsDevice device in devices) { // update a device Company tempCompany; Address tempAddress; Device currentDevice; if (deviceMap.ContainsKey(device.SerialNumber)) //update a device deviceMap.TryGetValue(device.SerialNumber, out currentDevice); else // insert a new device currentDevice = new Device(); currentDevice.SerialNumber = device.SerialNumber; currentDevice.SerialNumberTABS = device.SerialNumberTabs; currentDevice.Model = device.Model; if (device.CustomerAccountID != null && device.CustomerAccountID != "") { companyMap.TryGetValue(device.CustomerAccountID, out tempCompany); currentDevice.CustomerID = tempCompany.CompanyID; currentDevice.CustomerName = tempCompany.CompanyName; } if (companyMap.TryGetValue(device.ServicingDealerAccountID, out tempCompany)) currentDevice.CompanyID = tempCompany.CompanyID; currentDevice.StatusID = 1; currentDevice.Retries = 0; currentDevice.ControllerFamilyID = 1; if (currentDevice.EWBFrontPanelMsgOption == null) // set the Panel option to the default if it isn't set already currentDevice.EWBFrontPanelMsgOption = context.EWBFrontPanelMsgOptions.Where( i => i.OptionDescription.Contains("default")).Single(); // link the device to the existing address as long as it is actually an address if (addressMap.TryGetValue(GetAddressIdentifier(device.address), out tempAddress)) { if (GetAddressIdentifier(device.address) != "") currentDevice.Address = tempAddress; else currentDevice.Address = null; } else // insert a new Address and link the device to it (if not null) { if (GetAddressIdentifier(device.address) == "") currentDevice.Address = null; else { tempAddress = new Address(); tempAddress.Address1 = device.address.Address1; tempAddress.Address2 = device.address.Address2; tempAddress.Address3 = device.address.Address3; tempAddress.Address4 = device.address.Address4; tempAddress.City = device.address.City; tempAddress.Country = device.address.Country; tempAddress.PostalCode = device.address.PostalCode; tempAddress.State = device.address.State; addresses.AddObject(tempAddress); addressMap.Add(GetAddressIdentifier(tempAddress), tempAddress); currentDevice.Address = tempAddress; } } if (!deviceMap.ContainsKey(device.SerialNumber)) // if inserting, add to context { oldDevices.AddObject(currentDevice); deviceMap.Add(device.SerialNumber, currentDevice); } } context.SaveChanges();

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