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  • How to check results of LINQ to SQL query?

    - by rem
    In a WPF app I'd like to check if a return of a LINQ to SQL query contains some records, but my approach doesn't work: TdbDataContext context = new TdbDataContext(); var sh = from p in context.Items where p.Selected == true select p; if (sh == null) { MessageBox.Show("There are no Selected Items"); } Where am I wrong?

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  • How can I set default seed for all identities within a SQL Server database?

    - by Brandon DuRette
    Is there a way to tell SQL server to use specific default seed value for IDENTITY columns - assuming the (to be run) CREATE TABLE statements do not specify one? I don't really care about altering existing data or altering the seed values for specific IDENTITY columns. I want the same seed for all newly created identity columns. Assume I cannot modify the individual CREATE TABLE statements in any way.

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  • In SQL Server 2005, how can I use database_b, do something, then use the old db database_a in TSQL?

    - by Yousui
    Hi guys, In SQL Server 2005, how can I use database_b, do something, then use the old db database_a in TSQL? The following is my code but there is some problem with it. Who can help me to identity the problem? Great thanks. DECLARE @old_database_name VARCHAR(200) SET @old_database_name = db_name() use mydatabase create table t1(id int identity(1,1)) use @old_database_name

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  • More efficient SQL than using "A UNION (B in A)"?

    - by machinatus
    Edit 1 (clarification): Thank you for the answers so far! The response is gratifying. I want to clarify the question a little because based on the answers I think I did not describe one aspect of the problem correctly (and I'm sure that's my fault as I was having a difficult time defining it even for myself). Here's the rub: The result set should contain ONLY the records with tstamp BETWEEN '2010-01-03' AND '2010-01-09', AND the one record where the tstamp IS NULL for each order_num in the first set (there will always be one with null tstamp for each order_num). The answers given so far appear to include all records for a certain order_num if there are any with tstamp BETWEEN '2010-01-03' AND '2010-01-09'. For example, if there were another record with order_num = 2 and tstamp = 2010-01-12 00:00:00 it should not be included in the result. Original question: Consider an orders table containing id (unique), order_num, tstamp (a timestamp), and item_id (the single item included in an order). tstamp is null, unless the order has been modified, in which case there is another record with identical order_num and tstamp then contains the timestamp of when the change occurred. Example... id order_num tstamp item_id __ _________ ___________________ _______ 0 1 100 1 2 101 2 2 2010-01-05 12:34:56 102 3 3 113 4 4 124 5 5 135 6 5 2010-01-07 01:23:45 136 7 5 2010-01-07 02:46:00 137 8 6 100 9 6 2010-01-13 08:33:55 105 What is the most efficient SQL statement to retrieve all of the orders (based on order_num) which have been modified one or more times during a certain date range? In other words, for each order we need all of the records with the same order_num (including the one with NULL tstamp), for each order_num WHERE at least one of the order_num's has tstamp NOT NULL AND tstamp BETWEEN '2010-01-03' AND '2010-01-09'. It's the "WHERE at least one of the order_num's has tstamp NOT NULL" that I'm having difficulty with. The result set should look like this: id order_num tstamp item_id __ _________ ___________________ _______ 1 2 101 2 2 2010-01-05 12:34:56 102 5 5 135 6 5 2010-01-07 01:23:45 136 7 5 2010-01-07 02:46:00 137 The SQL that I came up with is this, which is essentially "A UNION (B in A)", but it executes slowly and I hope there is a more efficient solution: SELECT history_orders.order_id, history_orders.tstamp, history_orders.item_id FROM (SELECT orders.order_id, orders.tstamp, orders.item_id FROM orders WHERE orders.tstamp BETWEEN '2010-01-03' AND '2010-01-09') AS history_orders UNION SELECT current_orders.order_id, current_orders.tstamp, current_orders.item_id FROM (SELECT orders.order_id, orders.tstamp, orders.item_id FROM orders WHERE orders.tstamp IS NULL) AS current_orders WHERE current_orders.order_id IN (SELECT orders.order_id FROM orders WHERE orders.tstamp BETWEEN '2010-01-03' AND '2010-01-09');

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  • SerialPort ReadLine() after Thread.Sleep() goes crazy

    - by Mat
    Hi everybody, I've been fighting with this issue for a day and I can't find answer for it. I am trying to read data from GPS device trough COM port in Compact Framework C#. I am using SerialPort class (actually my own ComPort class boxing SerialPort, but it adds only two fields I need, nothing special). Anyway.. I am running while loop in a separate thread which reads line from the port, analyze NMEA data, print them, catch all exceptions and then I Sleep(200) the thread, cause I need CPU for other threads... Without Sleep it works fine, but uses 100% CPU.. When I dont use Sleep after few minutes the output from COM port looks like this: GPGSA,A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F GSA,A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F A,A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F ,18,12,271,24,24,05,020,24,14,04,326,25,11,03,023,*76 A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F 3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F 09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F ,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F as you can see the same message is read few times but cut. I wonder what I'm doing wrong... My port configuration: port.ReadBufferSize = 4096; port.BaudRate = 4800; port.DataBits = 8; port.Parity = Parity.None; port.StopBits = StopBits.One; port.NewLine = "\r\n"; port.ReadTimeout = 1000; port.ReceivedBytesThreshold = 100000; And my reading function: private void processGps(){ while (!closing) { //reconnect if needed try { string sentence = port.ReadLine(); //here print the sentence //analyze the sentence (this takes some time 50-100ms) } catch (TimeoutException) { Thread.Sleep(0); } catch (IOException ioex) { //handling IO exception (some info on the screen) } Thread.Sleep(200); } } There is some more stuff in this function like reconnection if the device is lost etc.. but it is not called when the GPS is connected properly.. I was trying port.DiscardInBuffer(); after some blocks of code (in TimeoutException, after read..) Did anyone had similar problem? I really dont know what I'm doing wrong.. The only way to get rig of it is removing the last Sleep... Thanks in advance! Best Regards, Mat

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  • In Protobuf-net how can I pass an array of type object with objects of different types inside, knowi

    - by cloudraven
    I am trying to migrate existing code that uses XmlSerializer to protobuf-net due to the increased performance it offers, however I am having problems with this specific case. I have an object[] that includes parameters that are going to be sent to a remote host (sort of a custom mini rpc facility). I know the set of types from which these parameters can be, but I cannot tell in advance in which order they are going to be sent. I have three constraints. The first is that I am running in Compact Framework, so I need something that works there. Second, as I mentioned performance is a big concern (on the serializing side) so I would rather avoid using a lot of reflection there if possible. And the most important is that I care about the order in which this parameters were sent. Using XmlSerializer it was easy just adding XmlInclude, but for fields there is nothing equivalent as far as I know in Protobuf-net. So, is there a way to do this? Here is a simplified example. [Serializable] [XmlInclude(typeof(MyType1)), XmlInclude(typeof(MyType2)), XmlInclude(typeof(MyType3)) public class Message() { public object[] parameters; public Message(object[] parms) { parameters = parms; } } Message m = new Message(new object[] {MyType1(), 33, "test", new MyType3(), new MyType3()}); MemoryStream ms = new MemoryStream(); XmlSerializer xml = new XmlSerializer(typeof(Message)); xml.Serialize(ms,xml); That will just work with XmlSerializer, but if I try to convert it to protobuf-net I will get a "No default encoding for Object" message. The best I came up with is to use generics and [ProtoInclude] as seen in this example. Since I can have different object types within the array this doesn't quite make it. I added a generic List for each potential type and a property with [ProtoIgnore] with type object[] to add them and get them. I have to use reflection when adding them (to know in which array to put each item) which is not desirable and I still can't preserve the ordering as I just extract all the items on each list one by one and put them into a new object[] array on the property get. I wonder if there is a way to accomplish this?

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  • Cross-database transactions from one SP

    - by Michael Bray
    I need to update multiple databases with a few simple SQL statement. The databases are configurared in SQL using 'Linked Servers', and the SQL versions are mixed (SQL 2008, SQL 2005, and SQL 2000). I intend to write a stored procedure in one of the databases, but I would like to do so using a transaction to make sure that each database gets updated consistently. Which of the following is the most accurate: Will a single BEGIN/COMMIT TRANSACTION work to guarantee that all statements across all databases are successful? Will I need multiple BEGIN TRANSACTIONS for each individual set of commands on a database? Are transactions even supported when updating remote databases? I would need to execute a remote SP with embedded transaction support. Note that I don't care about any kind of cross-database referential integrity; I'm just trying to update multiple databases at the same time from a single stored procedure if possible. Any other suggestions are welcome as well. Thanks!

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  • Question about DBD::CSB Statement-Functions

    - by sid_com
    From the SQL::Statement::Functions documentation: Function syntax When using SQL::Statement/SQL::Parser directly to parse SQL, functions (either built-in or user-defined) may occur anywhere in a SQL statement that values, column names, table names, or predicates may occur. When using the modules through a DBD or in any other context in which the SQL is both parsed and executed, functions can occur in the same places except that they can not occur in the column selection clause of a SELECT statement that contains a FROM clause. # valid for both parsing and executing SELECT MyFunc(args); SELECT * FROM MyFunc(args); SELECT * FROM x WHERE MyFuncs(args); SELECT * FROM x WHERE y < MyFuncs(args); # valid only for parsing (won't work from a DBD) SELECT MyFunc(args) FROM x WHERE y; Reading this I would expect that the first SELECT-statement of my example shouldn't work and the second should but it is quite the contrary. #!/usr/bin/env perl use warnings; use strict; use 5.010; use DBI; open my $fh, '>', 'test.csv' or die $!; say $fh "id,name"; say $fh "1,Brown"; say $fh "2,Smith"; say $fh "7,Smith"; say $fh "8,Green"; close $fh; my $dbh = DBI->connect ( 'dbi:CSV:', undef, undef, { RaiseError => 1, f_ext => '.csv', }); my $table = 'test'; say "\nSELECT 1"; my $sth = $dbh->prepare ( "SELECT MAX( id ) FROM $table WHERE name LIKE 'Smith'" ); $sth->execute (); $sth->dump_results(); say "\nSELECT 2"; $sth = $dbh->prepare ( "SELECT * FROM $table WHERE id = MAX( id )" ); $sth->execute (); $sth->dump_results(); outputs: SELECT 1 '7' 1 rows SELECT 2 Unknown function 'MAX' at /usr/lib/perl5/site_perl/5.10.0/SQL/Parser.pm line 2893. DBD::CSV::db prepare failed: Unknown function 'MAX' at /usr/lib/perl5/site_perl/5.10.0/SQL/Parser.pm line 2894. [for Statement "SELECT * FROM test WHERE id = MAX( id )"] at ./so_3.pl line 30. DBD::CSV::db prepare failed: Unknown function 'MAX' at /usr/lib/perl5/site_perl/5.10.0/SQL/Parser.pm line 2894. [for Statement "SELECT * FROM test WHERE id = MAX( id )"] at ./so_3.pl line 30. Could someone explaine me this behavior?

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  • How to get result size from an SQL query and check size

    - by Jimmy
    Hi I'm trying to write a piece of code for a simple verification method as part of a MVC. At present the SQL is not written as a prepared statement so obviously it is at risk to a SQL injection so any help in regards to writing the SQL as a prepared statement would be really helpful. The method which is in the User model. public boolean getLoginInfo() { try { DBAccess dbAccess = new DBAccess(); String sql = "SELECT username, password FROM owner WHERE username = '" + this.username + "'AND password = '" + this.password + "';"; dbAccess.close();dbAccess.executeQuery(sql); dbAccess.close(); return true; } catch (Exception e) { return false; } } I want to get the size of the result set which is generated by the SQL query and if the size of it is 1 return true else it's false. If you need more info on the rest of the MVC just post and I'll get it up here.

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