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  • How to pull a RANDOM and UNIQUE record from SQL via LINQ.

    - by Jeremy H
    Okay, I found lots of posts on SO about how to pull a RANDOM item from the database when using LINQ. There seems to be a couple of differnet ways to handle this. What I need to do though is pull a RANDOM item from the database that the user has not seen before. The data I am pulling from the database is very small. Is there any way I can just hit the database once for 1000 records and then randomly scroll through those? Should I put a cookie on the users system recording the IDs of which items they have seen, pull a random record, check to see if it is seen and if so, pull from the database again? That seems like performance issues just waiting to happen. I don't expect anyone to code it for me, I am just looking for concepts and pointing in the right direction of how I should go about this. Need more details? Just let me know!

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  • Is there limit of "join" or the "where" or length of SQL query ?

    - by Chetan sharma
    Actually i was trying to get data from elgg database based on multiple joins. It generated very big query with lots of JOIN statements and query never respond back. SELECT distinct e.* from test_entities e JOIN test_metadata m1 on e.guid = m1.entity_guid JOIN test_metastrings ms1 on ms1.id = m1.name_id JOIN test_metastrings mv1 on mv1.id = m1.value_id JOIN test_objects_entity obj on e.guid = obj.guid JOIN test_metadata m2 on e.guid = m2.entity_guid JOIN test_metastrings ms2 on ms2.id = m2.name_id JOIN test_metastrings mv2 on mv2.id = m2.value_id JOIN test_metadata m3 on e.guid = m3.entity_guid JOIN test_metastrings ms3 on ms3.id = m3.name_id JOIN test_metastrings mv3 on mv3.id = m3.value_id JOIN test_metadata m4 on e.guid = m4.entity_guid JOIN test_metastrings ms4 on ms4.id = m4.name_id JOIN test_metastrings mv4 on mv4.id = m4.value_id JOIN test_metadata m5 on e.guid = m5.entity_guid JOIN test_metastrings ms5 on ms5.id = m5.name_id JOIN test_metastrings mv5 on mv5.id = m5.value_id JOIN test_metadata m6 on e.guid = m6.entity_guid JOIN test_metastrings ms6 on ms6.id = m6.name_id JOIN test_metastrings mv6 on mv6.id = m6.value_id where ms1.string='expire_date' and mv1.string <= 1272565800 and ms2.string='homecity' and mv2.string LIKE "%dasf%" and ms3.string='schoolname' and mv3.string LIKE "%asdf%" and ms4.string='award_amount' and mv4.string <= 123 and ms5.string='no_of_awards' and mv5.string <= 7 and ms6.string='avg_rating' and mv6.string <= 2 and e.type = 'object' and e.subtype = 5 and e.site_guid = 1 and (obj.title like '%asdf%') OR (obj.description like '%asdf%') and ( (e.access_id = -2 AND e.owner_guid IN ( SELECT guid_one FROM test_entity_relationships WHERE relationship='friend' AND guid_two=5 )) OR (e.access_id IN (2,1) OR (e.owner_guid = 5) OR ( e.access_id = 0 AND e.owner_guid = 5 ) ) and e.enabled='yes') and ( (m1.access_id = -2 AND m1.owner_guid IN ( SELECT guid_one FROM test_entity_relationships WHERE relationship='friend' AND guid_two=5 )) OR (m1.access_id IN (2,1) OR (m1.owner_guid = 5) OR ( m1.access_id = 0 AND m1.owner_guid = 5 ) ) and m1.enabled='yes') and ( (m2.access_id = -2 AND m2.owner_guid IN ( SELECT guid_one FROM test_entity_relationships WHERE relationship='friend' AND guid_two=5 )) OR (m2.access_id IN (2,1) OR (m2.owner_guid = 5) OR ( m2.access_id = 0 AND m2.owner_guid = 5 ) ) and m2.enabled='yes') and ( (m3.access_id = -2 AND m3.owner_guid IN ( SELECT guid_one FROM test_entity_relationships WHERE relationship='friend' AND guid_two=5 )) OR (m3.access_id IN (2,1) OR (m3.owner_guid = 5) OR ( m3.access_id = 0 AND m3.owner_guid = 5 ) ) and m3.enabled='yes') and ( (m4.access_id = -2 AND m4.owner_guid IN ( SELECT guid_one FROM test_entity_relationships WHERE relationship='friend' AND guid_two=5 )) OR (m4.access_id IN (2,1) OR (m4.owner_guid = 5) OR ( m4.access_id = 0 AND m4.owner_guid = 5 ) ) and m4.enabled='yes') and ( (m5.access_id = -2 AND m5.owner_guid IN ( SELECT guid_one FROM test_entity_relationships WHERE relationship='friend' AND guid_two=5 )) OR (m5.access_id IN (2,1) OR (m5.owner_guid = 5) OR ( m5.access_id = 0 AND m5.owner_guid = 5 ) ) and m5.enabled='yes') and ( (m6.access_id = -2 AND m6.owner_guid IN ( SELECT guid_one FROM test_entity_relationships WHERE relationship='friend' AND guid_two=5 )) OR (m6.access_id IN (2,1) OR (m6.owner_guid = 5) OR ( m6.access_id = 0 AND m6.owner_guid = 5 ) ) and m6.enabled='yes') order by obj.title limit 0, 10 this is the query that i am running.

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  • How to find largest common sub-tree in the given two binary search trees?

    - by Bhushan
    Two BSTs (Binary Search Trees) are given. How to find largest common sub-tree in the given two binary trees? EDIT 1: Here is what I have thought: Let, r1 = current node of 1st tree r2 = current node of 2nd tree There are some of the cases I think we need to consider: Case 1 : r1.data < r2.data 2 subproblems to solve: first, check r1 and r2.left second, check r1.right and r2 Case 2 : r1.data > r2.data 2 subproblems to solve: - first, check r1.left and r2 - second, check r1 and r2.right Case 3 : r1.data == r2.data Again, 2 cases to consider here: (a) current node is part of largest common BST compute common subtree size rooted at r1 and r2 (b)current node is NOT part of largest common BST 2 subproblems to solve: first, solve r1.left and r2.left second, solve r1.right and r2.right I can think of the cases we need to check, but I am not able to code it, as of now. And it is NOT a homework problem. Does it look like?

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  • How do I set a SQL Server 2008 Reporting Services Template to a Default Font?

    - by David Stein
    I'm creating a new template to create reports from at a later date. I know how to create one, and I know where to save it. However, the problem is this. Everything that is created on the report uses the default font of Arial with a size of 10pt. I need to set mine to default to Tahoma 11pt. I can create a mock title, mock tables, etc and save those to Tahoma 11pt, but any new controls that are used on any version of this report will default back to Arial 10pt. How do I fix this?

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  • Using Kerberos authentication for SQL Server 2008

    - by vivek m
    I am trying to configure my SQL Server to use Kerberos authentication. My setup is like this - My setup is like this- I have 2 virtual PCs in a Windows XP Pro SP3 host. Both VPCs are Windows Server 2003 R2. One VPC acts as the DC, DNS Server, DHCP server, has Active Directory installed and the SQL Server default instance is also running on this VPC. The second VPC is the domain member and it acts as the SQL Server client machine. I configured the SPN on the SQL Server service account to get the Kerberos working. On the client VPC it seems like it is using Kerberos authentication (as desired)- C:\Documents and Settings\administrator.SHAREPOINTSVC>sqlcmd -S vm-winsrvr2003 1> select auth_scheme from sys.dm_exec_connections where session_id=@@spid 2> go auth_scheme ---------------------------------------- KERBEROS (1 rows affected) 1> but on the server computer (where the SQL Server instance is actually running) it looks like it is still using NTLM authentication- . This is not a remote instance, the sql server is local to this machine. C:\Documents and Settings\Administrator>sqlcmd 1> select auth_scheme from sys.dm_exec_connections where session_id=@@spid 2> go auth_scheme ---------------------------------------- NTLM (1 rows affected) 1> What can i do so that it uses Kerberos on the server computer as well ? (or is this something that I should not expect)

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  • Attach an entity that is not new, perhaps having been loaded from another DataContext. LINQ to SQL -

    - by soldieraman
    Alright How I got this error I got one application sitting on a server 2 users accessing this application - doing some bulk data processing . eg. entering values and then the application is working with another system to extract values for them and then saving. I can't recreate the error The error logs show: The error happend at the same time in both the application Both happend on a Attach/Submit (but two different functions) There is no way they are using the same DataContext object as I save the DataContext in the HttpContext.Items My hunch / guess is: One datacontext was not refreshed i.e. the an object was created for the same item twice as it was new in both the forms. eg. Customer Number - a customer was created (as one couldn't be found) by one datacontext - the other one couldn't find it either (i am using compiled queries to find it in the datacontext) so it created another object and on attaching failed. The HttpContext.Items lost its value somehow (i am using a virtual pc as server - maybe something went wrong there) I am going more of the second as I can't recreate the error - but it just might be a timing (for attach/save) thing - also the error makes me think of the 2nd too.

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  • LINQ Joins - Performance

    - by Meiscooldude
    I am curious on how exactly LINQ (not LINQ to SQL) is performing is joins behind the scenes in relation to how Sql Server performs joins. Sql Server before executing a query, generates an Execution Plan. The Execution Plan is basically an Expression Tree on what it believes is the best way to execute the query. Each node provides information on whether to do a Sort, Scan, Select, Join, ect. On a 'Join' node in our execution plan, we can see three possible algorithms; Hash Join, Merge Join, and Nested Loops Join. Sql Server will choose which algorithm to for each Join operation based on expected number of rows in Inner and Outer tables, what type of join we are doing (some algorithms don't support all types of joins), whether we need data ordered, and probably many other factors. Join Algorithms: Nested Loop Join: Best for small inputs, can be optimized with ordered inner table. Merge Join: Best for medium to large inputs sorted inputs, or an output that needs to be ordered. Hash Join: Best for medium to large inputs, can be parallelized to scale linearly. LINQ Query: DataTable firstTable, secondTable; ... var rows = from firstRow in firstTable.AsEnumerable () join secondRow in secondTable.AsEnumerable () on firstRow.Field<object> (randomObject.Property) equals secondRow.Field<object> (randomObject.Property) select new {firstRow, secondRow}; SQL Query: SELECT * FROM firstTable fT INNER JOIN secondTable sT ON fT.Property = sT.Property Sql Server might use a Nested Loop Join if it knows there are a small number of rows from each table, a merge join if it knows one of the tables has an index, and Hash join if it knows there are a lot of rows on either table and neither has an index. Does Linq choose its algorithm for joins? or does it always use one?

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  • SQL update fields of one table from fields of another one.

    - by Nir
    I'm having two tables: A [ID, column1, column2, column3] B [ID, column1, column2, column3, column4] A table will always be subset of B table (meaning all columns of A are also in B). I want to update a record with a specific ID in B with their data from A for all columns of A. This ID exists both in A and B. Is there an UPDATE syntax or any other way to do that without specifying the column names, just saying "set all columns of A"? I'm using postgresql, so a specific non-standard command is also accepted (however, not preferred). Thanks.

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  • How to grant permissions to single SELECT/UPDATE statment (sql server) ?

    - by Albert
    I have a problem when trying to execute this update statement (below) using C# SqlCommand when I execute it locally it works fine, but when deployed to another machine I got a permission error The SELECT permission was denied on the object Order ... The UPDATE permission was denied on the object Order ... Update Statement "UPDATE Order SET Request = @request WHERE Id = @ID"; Is there any way to add GRANT SELECT and GRANT UPDATE to a single statement like the update above without using a stored procedure? or the SP is the way to go on this? Thanks in advance

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  • How do I write a Oracle SQl query for this tricky question...

    - by atrueguy
    Here is the table data with the column name as Ships. +--------------+ Ships | +--------------+ Duke of north | ---------------+ Prince of Wales| ---------------+ Baltic | ---------------+ In the Outcomes table, transform names of the ships containing more than one space, as follows: Replace all characters between the first and the last spaces (excluding these spaces) by symbols of an asterisk (*). The number of asterisks must be equal to number

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  • Can I use SQL to update multiple rows with multiple values from another table?

    - by stu
    I've got a one to many table with ids and traits for those users. I want to copy one user's settings to another. userid trait onoff ------ ----- ----- 1 1 on 1 2 on 1 3 on 1 4 on 2 1 off 2 2 off 2 3 off 2 4 off So I want to copy the onoff values from user 1 to 2, so that user2 has everything on when I'm done. update table set onoff = (select onoff from table where userid=1) where userid=2 that's the basic idea, but obviously doesn't work. I imagine I want the server to think in terms of a correlated subquery, but the outer part isn't a query, it's an update. Is this even possible in one step?

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  • Dependency Injection -Colloquial explanation

    - by nettguy
    Recently I was asked to express the DI in colloquial explanation. I answered : 1) I am going to a hotel.I ordered food.The hotel management asks me to clean the plates and clean the tables.So here i am a client,I am responsible for managing the service (Instantiating,executing,disposing).But DI decouples such tasks so the service consumer no need not worry about controlling the life cycle of the service. 2) He also asked is there any microsoft API follows DI ?.I answered (This was my guess) In WCF you can create a Proxy using ChannelFactory that controls the life time of your factory. for item (1) he said only 10% is correct for item(2) he said that is factory pattern not dependency injection. Actually what went wrong in my explanation (apart from my bad English) ? What is the real answers for those? I am waiting for your valuable suggestions.

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  • What database strategy to choose for a large web application

    - by Snoopy
    I have to rewrite a large database application, running on 32 servers. The hardware is up to date, each machine has two quad core Xeon and 32 GByte RAM. The database is multi-tenant, each customer has his own file, around 5 to 10 GByte each. I run around 50 databases on this hardware. The app is open to the web, so I have no control on the load. There are no really complex queries, so SQL is not required if there is a better solution. The databases get updated via FTP every day at midnight. The database is read-only. C# is my favourite language and I want to use ASP.NET MVC. I thought about the following options: Use two big SQL servers running SQL Server 2012 to serve the 32 servers with data. On the 32 servers running IIS hosting providing REST services. Denormalize the database and use Redis on each webserver. Use booksleeve as a Redis client. Use a combination of SQL Server and Redis Use SQL Server 2012 together with Hadoop Use Hadoop without SQL Server What is the best way for a read-only database, to get the best performance without loosing maintainability? Does Map-Reduce make sense at all in such a scenario? The reason for the rewrite is, the old app written in C++ with ISAM technology is too slow, the interfaces are old fashioned and not nice to use from an website, especially when using ajax. The app uses a relational datamodel with many tables, but it is possible to write one accerlerator table where all queries can be performed on, and all other information from the other tables are possible by a simple key lookup.

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  • SQL? "Show me all the Activities that can be performed by User X."

    - by Casey Fulton
    I'm at my wits end. I've searched like crazy, read plenty of database textbooks and God knows how many online guides, blogs and forums. Can someone put me out of my misery? PseudoSchema Diagram (Warning: although pretty, not in a format even remotely approaching ER diagrams! Primary keys are bold, foreign keys are italics.) Given the above set of tables relating Users to Groups to Privileges, and then a set of Activities that can each require a Privilege to perform, how do you find out this: Show me all the Activities that can be performed by User X. That is: User X is a member of groups G and F; groups G and F correlate to privileges P, Q, R and S; show me all the activities that require privileges either P, Q, R or S. How do you do this?

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  • How do I make a sql query where fields are the result of a different query?

    - by CRP
    I have two tables, the first is like this: f1 | f2 | f3 | f4 ----------------- data.... the second contains info about the fields of the first: field | info ------------ f1 a f2 b f3 a etc. I would like to query the first table selecting the fields with a query on the second. So, for example, I might want to get data for fields where info is equal to "a", thus I would do "select f1, f3 from first_table". How do I do this programmatically? I was thinking about something along the lines of select (select fields from second_table where info='a') from first_table Thanks Chris

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