I'm trying to query some date from DB2/IBM AS400. for this purpose I've tested theses two libraries: Oledb and iDB2Command that iDB2Command is released by IBM in their iSerires package for .Net
when I execute the following command with iDB2Command, I get a command timeout exception:
using (iDB2Connection connection = new iDB2Connection("DATA SOURCE=0.0.0.0;USER ID=TEST;PASSWORD=TEST;CheckConnectionOnOpen=true;EnablePreFetch=false;"))
{
connection.Open();
iDB2Command cmd = new iDB2Command("SELECT DISTINCT * FROM LIB.Table1", connection);
cmd.CommandTimeout = 0;
DataTable dt = new DataTable();
iDB2DataAdapter da = new iDB2DataAdapter(cmd);
da.Fill(dt);
}
But when I use Oledb to execute the same query there is no problem and the query will be execute and returns some data.this is while if I remove "DISTINCT" keyword, the query will be executed with iDB2Command too. Similar to this problem is exists for UNION keywords and nested queries.
I even checked and config theses things, but the problem was not solved:
Increase QRYTIMLMT using CHGQRYA command
Uncheck "Allow Query Timeout" in "Odbc Datasource Administrator" for iSeries DSN.
Related
I have the following code to check if a table exists:
var selectQuery = $"SELECT count(*) FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = '{tableName}'";
using (var conn = new SqlConnection(_sqlServerConnectionString.SqlServerConnectionString))
{
conn.Open();
using (var cmd = new SqlCommand(selectQuery, conn))
{
var result = (int)cmd.ExecuteScalar();
return result > 0;
}
conn.Close();
}
this is called multiple times. On running this, I see:
The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.
What am I missing? I have closed connection so not sure what's missing?
This probably seems like a leak somewhere else. Also, if some kind of error is happening between your open and close code then your connections will keep piling up as the execution will not exit the using block.
Please refer this another stack overflow link:-
How can I solve a connection pool problem between ASP.NET and SQL Server?
I am wanting to delete all data from a table and reset the id column to 1. I want to do this in my controller, but i want to know the best way to do that. I have tried the SQLConnection/SQLCommand route, but have been unable to connect to the database successfully to do that. Is there a way like running a db.Clean function or something like that?
Updated
Here is how far it gets in the code:
string connectionString = "Data Source=(LocalDB)\v11.0;AttachDbFilename=c:\\Webs\\MvcFFL\\MvcFFL\\App_Data\\Players.mdf;Integrated Security=True";
string queryString = "Truncate table Players;";
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(queryString, connection);
connection.Open(); <- Fails here opening the connection
}
Then when it hits the connection.Open() here is the error:
An exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll but was not handled in user code Additional information: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
What can i do instead of this method?
You have an unescaped \in (LocalDB)\v11.0
You can change it to (LocalDB)\\v11.0, or else change the whole connection string to
#"Data Source=(LocalDB)\v11.0;AttachDbFilename=c:\Webs\MvcFFL\MvcFFL\App_Data\Players.mdf;Integrated Security=True" (notice the # and the lack of \\)
QUESTION: can YOU use multiple statements and recordset, which operate simultaneously, using the same connection in a non MULTI THREAD?
I only found this question which interests me, but the answer is not consistent.
JDBC Statement/PreparedStatement per connection
The answer explain the relationship between recordset and statement, which is known to me.
Given that, you can not have multiple recordsets for statement
The answer says that you can have multiple recordsets for connection. But they are not mentioned any other sources.
I'm asking if it's possible to loop over the first recordset, then using the same connection (used to generate first recordset) to open another recordset use it looping in iteration. And where is the documentation that define this behavior?
The situation that interests me is like this, the statement perform tasks simultaneously ins
Connection con = Factory.getDBConn (user, pss, endpoint, etc);
Statement stmt = con.createStatement ();
ResultSet rs = stmt.executeQuery ("SELECT TEXT FROM dba");
while (rs.next ()) {
rs.getInt (....
rs.getInt (....
rs.getInt (....
rs.getInt (....
Statement stmt2 con.createStatement = ();
ResultSet rs2 = stmt2.executeQuery ("iSelect ......");
while (rs2.next ()) {
....
rs2.close ();
stm2.close ();
Statement stmt3 con.createStatement = ();
ResultSet rs3 = stmt3.executeQuery ("Insert Into table xxx ......");
....
rs3.close ();
stm3.close ();
}
To clarify a bit more: with the execution of update in stmt3, you could obtain an error like this:
java.sql.SQLException: There is an open result set on the current connection, which must be closed prior to executing a query.
So you can't mix SQL in the same connection.
If I understand correctly, you need to work with two (or more) resultsets simmultaneously within a single method.
It is possible, and it works well. But you have to remember a few things:
Everything you do on each recordset is handled by a single Connection, unless you declare new connections for each Statement (and ResultSet)
If you need to do a multithreaded process, I suggest you to create a Connection for each thread (or use a connection pool); if you use a single connection in a multithreaded process, your program will hang or crash, since every SQL statement goes through a single connection, and every new statement has to wait until the previous one has finnished.
Besides that, your question needs some clarification. What do you really need to do?
A ResultSet object is automatically closed when the Statement object that generated it is closed, re-executed, or used to retrieve the next result from a sequence of multiple results.
http://docs.oracle.com/javase/6/docs/api/java/sql/ResultSet.html
SQL Server is a database that does support multiple record sets. So you can exceute a couple of queries in a single stored procedure for example
SELECT * FROM employees
SELECT * FROM products
SELECT * FROM depts
You can then move between each record set. At least I know you can do this in .Net for example
using (var conn = new SqlConnection("connstring"))
using (var command = new SqlCommand("SPName", conn))
{
conn.Open();
command.CommandType = CommandType.StoredProcedure;
var (reader = command.ExecuteReader())
{
while(reader.Read())
{
//Process all records from first result set
}
reader.Next();
while(reader.Read())
{
//Process all records from 2nd result set
}
reader.Next();
while(reader.Read())
{
//Process all records from 3rd result set
}
}
}
I am assuming that java would support a similar mechanism
I'm trying to connect to a SQL Anywhere 5 database (I know it's olllld!) with a .NET 3.5 app in WinXP and it works fine from a stand alone console app. But when I run the exact code in a plugin ,running off a separate AppDomain, (the only difference I can tell between the two) with the following code, I get the errors further below.
BTW Both are executed as the SAME user.
using (OdbcConnection connection =
new OdbcConnection(strConnect))
{
OdbcCommand command = new OdbcCommand(query, connection);
command.CommandType = CommandType.Text;
DataTable posRecordsTable = new DataTable();
connection.Open();
OdbcException Exception returns the following errors:
Index #0
Message: [Sybase][ODBC Driver]Unable to connect to database server: database engine not running
Index #1
Message: [Sybase][ODBC Driver]Invalid connection string attribute
Index #2
Message: [Sybase][ODBC Driver]Invalid connection string attribute
Index #3
Message: [Microsoft][ODBC Driver Manager] The driver doesn't support the version of ODBC behavior that the application requested (see SQLSetEnvAttr).
Does the driver on your AppDomain have the same configuration as your stand alone box? I think checking the similarity of the environments will help you. Usually such errors are resolved by looking at the config files from where the driver reads its information. Dont know much about SQL Anywhere, but in general, I've come across such issues and I fixed them by altering the connection information or the configuration file.
I am writing a stored procedure that when completed will be used to scan staging tables for bogus data on a column by column basis.
Step one in the exercise was just to scan the table --- which is what the code below does. The issue is that this code runs in 5:45 seconds --- however the same code run as a console app (changing the connectionstring of course) runs in about 44 seconds.
using (SqlConnection sqlConnection = new SqlConnection("context connection=true"))
{
sqlConnection.Open();
string sqlText = string.Format("select * from {0}", source_table.Value);
int count = 0;
using (SqlCommand sqlCommand = new SqlCommand(sqlText, sqlConnection))
{
SqlDataReader reader = sqlCommand.ExecuteReader();
while (reader.Read())
count++;
SqlDataRecord record = new SqlDataRecord(new SqlMetaData("rowcount", SqlDbType.Int));
SqlContext.Pipe.SendResultsStart(record);
record.SetInt32(0, count);
SqlContext.Pipe.SendResultsRow(record);
SqlContext.Pipe.SendResultsEnd();
}
}
However the same code (different connection string of course) runs in a console app in about 44 seconds (which is closer to what I was expecting on the client side)
What am I missing on the SP side, that would cause it to run so slow.
Please note: I fully understand that if I wanted a count of rows, I should use the count(*) aggregation --- that's not the purpose of this exercise.
The type of code you are writing is highly susceptible to SQL Injection. Rather than processing the reader like you are, you could just use the RecordsAffected Property to find the number of rows in the reader.
EDIT:
After doing some research, the difference you are seeing is a by design difference between the context connection and a regular connection. Peter Debetta blogged about this and writes:
"The context connection is written such that it only fetches a row at a time, so for each of the 20 million some odd rows, the code was asking for each row individually. Using a non-context connection, however, it requests 8K worth of rows at a time."
http://sqlblog.com/blogs/peter_debetta/archive/2006/07/21/context-connection-is-slow.aspx
Well it would seem the answer is in the connection string after all.
context connection=true
versus
server=(local); database=foo; integrated security=true
For some bizzare reason, using the "external" connection the SP runs almost as fast as a console app (still not as fast mind you! -- 55 seconds)
Of course now the assembly has to be deployed as External rather than Safe --- and that introduces more frustration.