&gt; READ COMMITTED is the default isolation level for the Microsoft SQL Server Database Engine.

Source:

- [Customizing Transaction Isolation Level @ MSDN][1].

Here is how it compares to other isolation levels:

- [Transaction Isolation Levels @ MSDN][2].

The MSDN documentation for `SqlConnection.BeginTransaction()` also states `Read committed`

&gt; ... To reset the isolation level to the default (READ COMMITTED) ...

* [MSDN article](https://msdn.microsoft.com/en-us/library/5ha4240h%28v=vs.110%29.aspx?f=255&amp;MSPPError=-2147217396)

  [1]: http://msdn.microsoft.com/en-us/library/ms175909.aspx
  [2]: http://msdn.microsoft.com/en-us/library/ms709374%28v=vs.85%29.aspx

The accepted answer by hkf gives the correct answer for transactions started *manually* with `SqlConnection.BeginTransaction()`. Here, the default level is **ReadCommitted**.

However, this is not the only way to start a new transaction in ADO.NET: Transactions can also be created *automatically* by using the classes from the `System.Transactions` namespace, in particular, by creating a `TransactionScope`.

Contrary to transactions started manually, transactions created by the `System.Transactions` infrastructure (and, thus, by a `TransactionScope`) are **Serializable**.

See below link for more information:

- [IsolationLevel Enumeration @ MSDN][1].

  [1]: http://msdn.microsoft.com/en-us/library/system.transactions.isolationlevel%28v=vs.110%29.aspx

I am using rsa key to encrypt a long string which I will send to my server(will encrypt it with server&#39;s public key and my private key) But it throws an exception like `javax.crypto.IllegalBlockSizeException: Data must not be longer than 256 bytes` 
I feel that I have not understood the working of rsa properly till now(using the inbuilt libraries are the cause for this).&lt;br&gt; Can some one please explain why this exception is being thrown. Is it not at all possible to send long string encrypted?

getting a IllegalBlockSizeException: Data must not be longer than 256 bytes when using rsa

When I define this function,

    template&lt;class A&gt;
    set&lt;A&gt; test(const set&lt;A&gt;&amp; input) {
    	return input;
    }

I can call it using `test(mySet)` elsewhere in the code without having to explicitly define the template type. However, when I use the following function:

    template&lt;class A&gt;
    set&lt;A&gt; filter(const set&lt;A&gt;&amp; input,function&lt;bool(A)&gt; compare) {
    	set&lt;A&gt; ret;
    	for(auto it = input.begin(); it != input.end(); it++) {
    		if(compare(*it)) {
    			ret.insert(*it);
    		}
    	}
    	return ret;
    }

When I call this function using `filter(mySet,[](int i) { return i%2==0; });`
I get the following error:

&gt; error: no matching function for call to ‘filter(std::set&lt;int&gt;&amp;, main()::&lt;lambda(int)&gt;)’

However, all of these versions *do* work:

    std::function&lt;bool(int)&gt; func = [](int i) { return i%2 ==0; };
    set&lt;int&gt; myNewSet = filter(mySet,func);

    set&lt;int&gt; myNewSet = filter&lt;int&gt;(mySet,[](int i) { return i%2==0; });

    set&lt;int&gt; myNewSet = filter(mySet,function&lt;bool(int)&gt;([](int i){return i%2==0;}));

Why is c++11 unable to guess the template type when I put the lambda function directly inside the expression without directly creating a `std::function`?

**EDIT:**

Per advice of Luc Danton in the comments, here is an alternative to the function I had earlier that does not need the templates to be passed explicitly.

    template&lt;class A,class CompareFunction&gt;
    set&lt;A&gt; filter(const set&lt;A&gt;&amp; input,CompareFunction compare) {
    	set&lt;A&gt; ret;
    	for(auto it = input.begin(); it != input.end(); it++) {
    		if(compare(*it)) {
    			ret.insert(*it);
    		}
    	}
    	return ret;
    }

This can be called by `set&lt;int&gt; result = filter(myIntSet,[](int i) { i % 2 == 0; });` without needing the template.

The compiler can even guess the return types to some extent, using the new decltype keyword and using the new function return type syntax. Here is an example that converts a set to a map, using one filtering function and one function that generates the keys based on the values:

    template&lt;class Value,class CompareType,class IndexType&gt;
    auto filter(const set&lt;Value&gt;&amp; input,CompareType compare,IndexType index) -&gt; map&lt;decltype(index(*(input.begin()))),Value&gt; {
    	map&lt;decltype(index(*(input.begin()))),Value&gt; ret;
    	for(auto it = input.begin(); it != input.end(); it++) {
    		if(compare(*it)) {
    			ret[index(*it)] = *it;
    		}
    	}
    	return ret;
    }

It can also be called without using the template directly, as

    map&lt;string,int&gt; s = filter(myIntSet,[](int i) { return i%2==0; },[](int i) { return toString(i); });

C++11 does not deduce type when std::function or lambda functions are involved

What is the default transaction isolation level for SQL Server with ADO.NET? I am using a default installation of SQL Server and just the normal System.Data.SqlClient classes.

What is the default transaction isolation level for SQL Server with ADO.NET?

<p>What is the default transaction isolation level for SQL Server with ADO.NET? I am using a default installation of SQL Server and just the normal System.Data.SqlClient classes.</p>


Improve SQL Server query performance on large tables

How to fetch the data from one database and insert in to another database table? I can&#39;t to do this. Please help me in transferring data from one to another.

Transfer data from one database to another database

I have this, and i get an error at set total.
Why can&#39;t i access a cte many times?

    ALTER PROCEDURE [dbo].[GetLeaguePlayers]
    (
    	@idleague int,
    	@pageNumber int,
    	@pageSize int,
    	@total int OUTPUT
    )
    AS
    WITH CTEPlayers AS
    (
    	SELECT ROW_NUMBER() OVER (ORDER BY p.Name) AS RowNumber, p.Id, p.Name, t.Name AS Team
    	FROM Players p INNER JOIN Teams t ON p.IdTeam=t.Id INNER JOIN Leagues l ON l.Id=t.IdLeague
    	WHERE l.Id=@idleague
    )
    SELECT Id, Name
    FROM CTEPlayers c
    WHERE RowNumber&gt;@pageSize*(@pageNumber-1) AND RowNumber&lt;@pageSize*@pageNumber;
    SET @total = ( SELECT COUNT(*) FROM CTEPlayers )

Use one CTE many times

When using this statement

    create table demo (
        ts timestamp
    )

    insert into demo select current_timestamp

I get the following error:

&gt;Cannot insert an explicit value into a timestamp column. Use INSERT with a column list to exclude the timestamp column, or insert a DEFAULT into the timestamp column

How do I insert the current time to a `timestamp` column?

SQL Server: Cannot insert an explicit value into a timestamp column

I have a table called `countries` and I define the `country_name` column to be unique by creating a “Index/Key” of type “Unique Key” on SQL Server 2008 R2. 

But I have the following questions:

1. will creating “Index/Key” of type “Unique Key” automatically create a non-clustered index on this column?
2. if I change the type from being “Unique Key” to &quot;Index&quot; and I keep the `IsUnique` value to be &quot;Yes&quot;,, then will there be any differences ?
3. so why there are two options “Unique Key” and &quot;Index&quot; I think the two are the same ?

Unique key vs. unique index on SQL Server 2008

I have 2 commands and need both of them executed correctly or none of them executed. So I think I need a transaction, but I don&#39;t know how to use it correctly.

What&#39;s the problem with the following script?
    
    BEGIN TRANSACTION [Tran1]

    INSERT INTO [Test].[dbo].[T1]
        ([Title], [AVG])
    VALUES (&#39;Tidd130&#39;, 130), (&#39;Tidd230&#39;, 230)

    UPDATE [Test].[dbo].[T1]
      SET [Title] = N&#39;az2&#39; ,[AVG] = 1
      WHERE [dbo].[T1].[Title] = N&#39;az&#39;

    COMMIT TRANSACTION [Tran1]
    GO

The `INSERT` command is executed, but the `UPDATE` command has a problem.

How can I implement this to rollback both commands if any of them have an error in execution?

Correct use of transactions in SQL Server

I would like to run multiple insert statements on multiple tables. I am using dapper.net. I don&#39;t see any way to handle transactions with dapper.net.

Please share your ideas on how to use transactions with dapper.net.


How to use transactions with dapper.net?

Please help me understand the use-case behind `SELECT ... FOR UPDATE`.

**Question 1**: Is the following a good example of when `SELECT ... FOR UPDATE` should be used?

Given:

* rooms[id]
* tags[id, name]
* room_tags[room_id, tag_id]
  * room_id and tag_id are foreign keys

The application wants to list all rooms and their tags, but needs to differentiate between rooms with no tags versus rooms that have been removed. If SELECT ... FOR UPDATE is not used, what could happen is:

* Initially:
  * rooms contains `[id = 1]`
  * tags contains `[id = 1, name = &#39;cats&#39;]`
  * room_tags contains `[room_id = 1, tag_id = 1]`
* Thread 1: `SELECT id FROM rooms;`
  * `returns [id = 1]`
* Thread 2: `DELETE FROM room_tags WHERE room_id = 1;`
* Thread 2: `DELETE FROM rooms WHERE id = 1;`
* Thread 2: [commits the transaction]
* Thread 1: `SELECT tags.name FROM room_tags, tags WHERE room_tags.room_id = 1 AND tags.id = room_tags.tag_id;`
  * returns an empty list

Now Thread 1 thinks that room 1 has no tags, but in reality the room has been removed. To solve this problem, Thread 1 should `SELECT id FROM rooms FOR UPDATE`, thereby preventing Thread 2 from deleting from `rooms` until Thread 1 is done. Is that correct?

**Question 2**: When should one use `SERIALIZABLE` transaction isolation versus `READ_COMMITTED` with `SELECT ... FOR UPDATE`?

Answers are expected to be portable (not database-specific). If that&#39;s not possible, please explain why.

When to use SELECT ... FOR UPDATE?

What is the difference between non-repeatable read and phantom read?

I have read the [Isolation (database systems) article from Wikipedia](http://en.wikipedia.org/wiki/Isolation_(database_systems)), but I have a few doubts. In the below example, what will happen: the **non-repeatable read** and **phantom read**?

####**Transaction A**

    SELECT ID, USERNAME, accountno, amount FROM USERS WHERE ID=1

####**OUTPUT:**

    1----MIKE------29019892---------5000

####**Transaction B**

    UPDATE USERS SET amount=amount+5000 where ID=1 AND accountno=29019892;
    COMMIT;

####**Transaction A**

    SELECT ID, USERNAME, accountno, amount FROM USERS WHERE ID=1

Another doubt is, in the above example, which isolation level should be used? And why?

What is the difference between Non-Repeatable Read and Phantom Read?

I can&#39;t understand the behavior difference between the `PROPAGATION_REQUIRES_NEW` and `PROPAGATION_NESTED` propagation policies. It seems to me that in both cases, the current process is rollbacked but not the whole transaction. Any clue?

Differences between requires_new and nested propagation in Spring transactions

I am trying to save Employee details, which has references with City. But everytime I try to save my contact, which is validated I get the exception **&quot;ADO.Net Entity Framework An entity object cannot be referenced by multiple instances of IEntityChangeTracker&quot;**

I had read so many post but still not getting the exact idea of what to do...
my Save button click code is given below

    protected void Button1_Click(object sender, EventArgs e)
        {
            EmployeeService es = new EmployeeService();
            CityService cs = new CityService();
    
            DateTime dt = new DateTime(2008, 12, 12);
            Payroll.Entities.Employee e1 = new Payroll.Entities.Employee();
         
            Payroll.Entities.City city1 = cs.SelectCity(Convert.ToInt64(cmbCity.SelectedItem.Value));
    
            e1.Name = &quot;Archana&quot;;
            e1.Title = &quot;aaaa&quot;;
            e1.BirthDate = dt;
            e1.Gender = &quot;F&quot;;
            e1.HireDate = dt;
            e1.MaritalStatus = &quot;M&quot;;
            e1.City = city1;        
    
            es.AddEmpoyee(e1,city1);
        }

and **Employeeservice Code**


    public string AddEmpoyee(Payroll.Entities.Employee e1, Payroll.Entities.City c1)
            {
                Payroll_DAO1 payrollDAO = new Payroll_DAO1();
                payrollDAO.AddToEmployee(e1);  //Here I am getting Error..
                payrollDAO.SaveChanges();
                return &quot;SUCCESS&quot;;
            }

entity object cannot be referenced by multiple instances of IEntityChangeTracker. while adding related objects to entity in Entity Framework 4.1

How to pass table valued parameter to stored procedure using ADO.NET?

Pass table valued parameter using ADO.NET

I do not want to split connection strings using string manipulation functions to get Server, Database, Username, and Password.

I read the following link and read the accepted answer, I found that is the best way to get username and password out from connection string, but what about Database Name? 

https://stackoverflow.com/questions/9975122/right-way-to-get-username-and-password-from-connection-string

How to get Database Name from Connection String using SqlConnectionStringBuilder. (does the DataSource is the Server name?)

How to get Database Name from Connection String using SqlConnectionStringBuilder

I get the following error on `cmd.ExecuteNonQuery`.

&gt; &quot;ExecuteNonQuery requires the command to have a transaction when the
&gt; connection assigned to the command is in a pending local transaction. 
&gt; The Transaction property of the command has not been initialized.&quot;

Here is my code:

	  //if (hdRefresh.Value.Length &gt; done.Value.Length || done.Value == &quot;1&quot;)
        //{
        //    //Write Your Add Customer Code here &gt; Response.Write(&quot;true&quot;) 
        //    done.Value = hdRefresh.Value;
        //}
        //else
        //{
        //    Response.Redirect(&quot;~/Cashier/BTBill.aspx&quot;);
        //    return;
        //}

        if (IsClosedToDay())
        {
            ScriptManager.RegisterClientScriptBlock(Page, typeof(Page), &quot;Warning&quot;, &quot;&lt;script&gt;alert(&#39;Day Closing has been Performed &#39;)&lt;/script&gt;&quot;, false);
            return;
        }

        DateTime dateFeomDB = getdate();
        // by atizaz
        if (HDD.Value == &quot;&quot; || HDD.Value == null)
        {
            ScriptManager.RegisterClientScriptBlock(Page, typeof(Page), &quot;Warning&quot;, &quot;&lt;script&gt;alert(&#39;No Transaction Found&#39;)&lt;/script&gt;&quot;, false);
            return;
        }
        //
        SqlConnection scon = new SqlConnection(ConfigurationManager.ConnectionStrings[&quot;SQLCONN&quot;].ToString());
        Common.BillTransaction bill1 = new Common.BillTransaction();
        ProcessUpdateBalandUnAuthBal insertBalance = new ProcessUpdateBalandUnAuthBal();
        Common.Currency currencyy = new Common.Currency();
        ProcessAuthorizeTokenByBillNo authorize = new ProcessAuthorizeTokenByBillNo();
        BillTransaction bill = new BillTransaction();
        scon.Open();
        SqlTransaction sqlTrans = scon.BeginTransaction();
        try
        {
            string strforxml = HDD.Value;
            XmlDocument docXml = new XmlDocument();


            #region Read In To Sender Controlls

            #region Common Information
            Contact con = new Contact();
            con.Title = ddlTitle.SelectedItem.Text;
            con.FirstName = TextBox1.Text.Trim();
            con.LastName = TextBox9.Text.Trim();
            con.ConTactNo = txtCell.Text == &quot;&quot; ? SqlString.Null : txtCell.Text;
            con.Country = ddlCountry.SelectedItem.Text;
            con.CustomerType = ddlCustomerType.SelectedItem.Text;
            con.CustTypeID = int.Parse(ddlCustomerType.SelectedValue);
            con.CountryID = Int32.Parse(ddlCountry.SelectedValue);
            con.sqlTransaction = sqlTrans;
            if (Scitytxt.Value != &quot;&quot;)
            {
                try
                {
                    con.City = Scitytxt.Value;
                    con.CityID = Int32.Parse(Scityval.Value);
                }
                catch (Exception)
                { }
            }
            else
            {
                con.City = SqlString.Null;// Scitytxt.Value;
                con.CityID = SqlInt32.Null;// Int32.Parse(Scityval.Value);
                con.Address = &quot;&quot;;
            }
            //con.City = ddlCity.SelectedItem.Text;
            //con.CityID = int.Parse(ddlCity.SelectedValue);
            con.Address = TextBox10.Text;
            #endregion

            #region Check For NIC and Passport

            if (txtNIC.Text != &quot;&quot; || txtPassport.Text != &quot;&quot;)
            {
                SqlDataReader rdrsender;

                if (txtNIC.Text != &quot;&quot;)
                {
                    con.NIC = txtNIC.Text;
                }
                else
                {
                    con.NIC = SqlString.Null;
                }
                if (txtPassport.Text != &quot;&quot;)
                {
                    con.Passport = txtPassport.Text;
                }
                else
                {
                    con.Passport = SqlString.Null;
                }
                ProcessSearchContactInContactInfo srchSender = new ProcessSearchContactInContactInfo();
                srchSender.Contact = con;
                srchSender.Invokewith5parameters();
                rdrsender = srchSender.ResultSet;

                #region If record Doesnot Exist In response of NIC Passport
                if (!rdrsender.Read())
                {
                    rdrsender.Close();
                    rdrsender.Dispose();
                    //  con.sqlTransaction = sqlTrans;
                    ProcessAddContact InsertnewSenderInfo = new ProcessAddContact();
                    // InsertnewSenderInfo.sqlTransaction = sqlTrans;
                    InsertnewSenderInfo.Contact = con;
                    InsertnewSenderInfo.Invoke();
                    
                    //  sender1 = InsertnewSenderInfo.ResultSet;
                    //  Sender_ID.Value = sender1[13].ToString();
                }
                #endregion
                #region If Record Exists
                else
                {
                    con.CustomerID = Int32.Parse(rdrsender[&quot;Customer_ID&quot;].ToString());
                    rdrsender.Close();
                    rdrsender.Dispose();
                }
                #endregion
            }
            #endregion

            #region If Customer Donot Have NIC And/OR Passport
            else// this executes when both Pasport and NIC are Null
            {
                con.NIC = SqlString.Null;
                con.Passport = SqlString.Null;
                ProcessAddContact InsertnewSenderInfo = new ProcessAddContact();
                InsertnewSenderInfo.Contact = con;
                InsertnewSenderInfo.Invoke();

                DataSet ds = new DataSet();
                int a = con.CustomerID;
                StringReader inforeader = new StringReader(&quot;&lt;CusTable&gt;&lt;CusInfo&gt;&lt;Relation_Type&gt;&lt;/Relation_Type&gt;&lt;HusbandFather_Name&gt;&lt;/HusbandFather_Name&gt;&lt;Address_Present&gt;&lt;/Address_Present&gt;&lt;Address_Other&gt;&lt;/Address_Other&gt;&lt;Phone_No_Office&gt;&lt;/Phone_No_Office&gt;&lt;Cell_No&gt;&lt;/Cell_No&gt;&lt;Fax_No&gt;&lt;/Fax_No&gt;&lt;Date_Of_Birth&gt;&lt;/Date_Of_Birth&gt;&lt;NTN_No&gt;&lt;/NTN_No&gt;&lt;Nationality&gt;&lt;/Nationality&gt;&lt;Occupation&gt;&lt;/Occupation&gt;&lt;Relation_With_Financial_Institution&gt;&lt;/Relation_With_Financial_Institution&gt;&lt;Other_Relation_With_Financial_Institution&gt;&lt;/Other_Relation_With_Financial_Institution&gt;&lt;Business_Relation&gt;&lt;/Business_Relation&gt;&lt;/CusInfo&gt;&lt;/CusTable&gt;&quot;);
                ds.ReadXml(inforeader);
                ds.GetXml();
                SqlCommand cmd = new SqlCommand(&quot;update Contact_Info set CustInfo=&quot; + ds.GetXml() + &quot; WHERE Customer_ID=&quot; + a + &quot;&quot;, scon);
                cmd.ExecuteNonQuery();
                
                //  sender1 = InsertnewSenderInfo.ResultSet;
                //  Sender_ID.Value = sender1[13].ToString();
            }

tell me what is problem in my code and how to solve it.

ExecuteNonQuery requires the command to have a transaction error in my code

I am updating a quantity in my cart, but it is throwing a Sequence has no elements&#39; exception.

And I don&#39;t know what that even means. At first I thought that maybe there was a null value being passed somewhere, but that isn&#39;t the case, as I&#39;ve checked that:


&gt; Sequence contains no elements    Description: An unhandled exception
&gt; occurred during the execution of the current web request. Please
&gt; review the stack trace for more information about the error and where
&gt; it originated in the code. 
&gt; 
&gt;  Exception Details: System.InvalidOperationException: Sequence
&gt; contains no elements
&gt; 
&gt; Source Error: 
&gt; 
&gt; 
&gt; 
&gt; Line 35:                 var uid = WebSecurity.CurrentUserId; Line 36:
&gt; var newqty = Request.Form[&quot;Quantity&quot;]; Line 37:                
&gt; OModel.Cart c = (from item in database.Carts Line 38:                 
&gt; where item.UserId == uid &amp;&amp; item.PartNumber == pnumber &amp;&amp; item.OrderId
&gt; == oid Line 39:                                    select item).First();


Any ideas what could be causing this?

Content Type	Original Author	Original Content on Stackoverflow
Question	Jonathan Allen	View Question on Stackoverflow
Solution 1 - Sql Server-2008	hkf	View Answer on Stackoverflow
Solution 2 - Sql Server-2008	user2818985	View Answer on Stackoverflow

What is the default transaction isolation level for SQL Server with ADO.NET?

Sql Server-2008 Problem Overview

Sql Server-2008 Solutions

Solution 1 - Sql Server-2008

Solution 2 - Sql Server-2008

C++11 does not deduce type when std::function or lambda functions are involved

getting a IllegalBlockSizeException: Data must not be longer than 256 bytes when using rsa

Attributions