从 C# 中的插入查询返回 ID

Question

I had problem that how to return auto incremented id of table when record is inserted in table using C# and MS Access database. The following is the code that I tried.

string data1 = string.Format("insert into Enquiry(fname,mname,lname,date_of_enq,address,contact_no,email_id,course_id,other,probable_date,updated_date,status)values('{0}','{1}','{2}','{3}','{4}','{5}','{6}','{7}','{8}','{9}','{10}','{11}')", 
        txtfName.Text, txtmName.Text, txtlName.Text, fullDate.Text, txtaddress.Text, txtContactNo.Text, varemail, CBCourse.SelectedValue.ToString(), txtOther.Text, DTPFeedBackDate.Text, updated_date, status);

I want the id of that inserted record which is auto incremented in table. How can I get it?

Answer 1

You can use following:

Select Ident_Current(TableName); 

SELECT @@IDENTITY;

SELECT SCOPE_IDENTITY();

SELECT @@IDENTITY It returns the last IDENTITY value produced on a connection, regardless of the table that produced the value, and regardless of the scope of the statement that produced the value. @@IDENTITY will return the last identity value entered into a table in your current session. While @@IDENTITY is limited to the current session, it is not limited to the current scope. If you have a trigger on a table that causes an identity to be created in another table, you will get the identity that was created last, even if it was the trigger that created it.

SELECT SCOPE_IDENTITY() It returns the last IDENTITY value produced on a connection and by a statement in the same scope, regardless of the table that produced the value. SCOPE_IDENTITY(), like @@IDENTITY, will return the last identity value created in the current session, but it will also limit it to your current scope as well. In other words, it will return the last identity value that you explicitly created, rather than any identity that was created by a trigger or a user defined function.

SELECT IDENT_CURRENT('tablename') It returns the last IDENTITY value produced in a table, regardless of the connection that created the value, and regardless of the scope of the statement that produced the value. IDENT_CURRENT is not limited by scope and session; it is limited to a specified table. IDENT_CURRENT returns the identity value generated for a specific table in any session and any scope.

To avoid the potential problems associated with adding a trigger later on, always use SCOPE_IDENTITY() to return the identity of the recently added row in your T SQL Statement or Stored Procedure.

In MsAccess

// Include a variable and a command to retrieve the identity value from the Access database.
int newID = 0;
OleDbCommand idCMD = new OleDbCommand("SELECT @@IDENTITY", nwindConn);
// Retrieve the identity value and store it in the CategoryID column.
newID = (int)idCMD.ExecuteScalar();
return newID;

Answer 2

just add eg SELECT @@IDENTITY to your query, and execute this as a scalar (be aware, that there are other ways, depending on the scope of your identity)

this applies to mssql - for other systems i am awaiting your answer on my comment!

btw: i would not execute a query in this way - the keyword is sql-injection. rather go for parameters!

Answer 3

this C# code worked for me using the Oracle.ManagedDataAccess 4.121.1.0 library:

OracleConnection conn = oracleConnLicen();
OracleCommand cmd = conn.CreateCommand();

conn.Open();
cmd.CommandText = "INSERT INTO account (name) VALUES ('Adam') RETURNING id INTO :p_id";

Then before ExecuteNonQuery:

OracleParameter pId = new OracleParameter("p_id", OracleDbType.Int32)
    {
        Direction = ParameterDirection.Output
    };
cmd.Parameters.Add(pId);

cmd.ExecuteNonQuery();
return Convert.ToInt32(pId.Value.ToString());