This is a general question that I can't seem to find any specific answer to. I am using a node module: https://www.npmjs.com/package/odbc
The module says to install a ODBC driver for the specified database and also have a properly configured odbc.ini and odbcinst.ini.
I am also using docker to run my node script.
My question is on my docker container, do I install each driver for the database? And then on the database server I have to configure the odbc.ini? Or on my node server I set this up? Or does it already come pre configured on some databases?
I keep getting the error: "Data source name not found, and no default driver specified"
Which I am guessing since I probably don't have the driver setup in my node container and the odbc.ini properly setup on my database server.
I am currently testing on a mysql database but want to be able to connect to any ODBC database.
Here is a link to setup mysql on ubuntu:
http://www.kaffeetalk.de/how-to-setup-and-configure-mysql-with-unixodbc-under-ubuntu-14-04/
odbc.ini contains DSN (Data Source Name) definitions, which are based on drivers registered in the odbcinst.ini, both found along with the drivers themselves on the ODBC data consuming host/environment (here, your docker container). These configuration files are typically (and optimally) respectively targeted by $ODBCINI and $ODBCINSTINI environment variables, but sometimes found at default locations like /etc/odbc.ini or ~/.odbc.ini.
You might look at some documentation, like the ODBC spec on MSDN, or developer guidance on iODBC.org. Do be sure to use ODBC's DBMS-agnostic SQL syntax for your queries, and not the DBMS-specific dialect for MySQL (or any other DBMS)!
Related
"SELECT name FROM master.sys.databases WHERE name NOT IN ('master', 'tempdb', 'model', 'msdb')"
In SQL server this above command used to retrieve the database list.
similarly, what is the command to retrieve the database list in DB2 using python program?
db2 server platform : windows
database : catalogued
With Db2-LUW, you do not use SQL to detect which databases are available, instead that is done via commands, although other methods are available.
For Db2-LUW with catalogued databases, you can use python to read the database directory by parsing the output of the command db2 list db directory assuming that you have a Db2-client which includes the db2 command line processor.
Note that non-IBM (third party) Db2-clients might have other functionality, so this answer only concerns Db2 clients supplied from IBM that include the Db2 CLP program.
You will need to understand the legacy concepts of catalogued databases , all of which are explained in the free online Db2 Knowledge Centre. See commands (non-SQL) list database directory and catalog database and catalog tcpip node etc.
If your databases are not catalogued in the database directory, but instead are configured in XML file called db2dsdriver.cfg or equivalent, then you cannot use this method, although you can parse the XML file looking for DATABASE and DSN stanzas.
Additionally, if your databases are on i-series , then different considerations apply for IBM i access databases.
There is a sample code here, in the function query_sdb_dir (you can parse the output of the command db2 list db directory ). BUT this assumes that you have a Db2 client installed that includes the Db2 CLP (i.e on MS-Windows, that you have db2.exe on the PATH, this is the command line processor CLP). By default with Python ibm_db you do not get this executable because it is not part of the tiny footprint CLIDRIVER that comes by default with the python ibm_db module. But you can first install a Db2-driver that includes the CLP (db2.exe on MS-Windows), set environment variable IBM_DB_HOME to point to its installation location, then pip install ibm_db and it will use your pre-existing Db2-driver and will not install the default clidriver.
There are other ways, typically that involve a database connection and using the monitoring functionality. But the discovery action (without a database connection) seems to be the topic of your question.
The following statement (if you have permissions to use these table functions) returns a list of active databases managed by the same Db2 for LUW instance, which manages the database you are connected to.
-- Preferred method since Db2 9.7
SELECT DISTINCT DB_NAME
FROM TABLE (MON_GET_MEMORY_SET ('DATABASE', NULL, -2))
-- For Db2 versions before 9.7
SELECT DISTINCT DB_NAME
FROM TABLE (SNAP_GET_DB (NULL))
You won't see non-active databases (if any) in this list.
I have been working with python and postgreql for over a year. I can connect and work with postgres databases by blindly using various libraries. But whenever I change platform (most recently from macOS laptop to remote ubuntu server) I go through a day or so of trying to get libraries working eg. I was using 'pyodbc' in some modules but when I migrated the code to the server I had to switch to 'pg8000' because the modules as they were kept throwing errors.
Can someone explain or point me to a link explaining how python connects to dB's? For example, why do I need a MS ODBC driver for 'pyodbc' to connect to an Azure SQL or postgresql but 'pg8000' seems to need nothing at all to connect to a postgresql? When I move to an Ubuntu environment and install ODBC drivers they show up on root under /etc, and /opt (for MS ODBC) but also in my Conda environment (/anaconda3/envs/) and I don't know which is the correct choice for 'ODBC.ini'?
Like I say, I can get things working but really have no understanding as to why they are working and that means I waste time experimenting every time I deal with a change in environment. I've not yet found an explanation online that covers more than a very specific circumstance eg. 'here's how to install our driver ...' Any help would be appreciated.
Final Update:
Following the responses esp. #Thompson the diagram below seems to be the final interpretation and I have a better idea of where to look for answers. For the record pyodbc, SQLAlchemy and pg8000 have been my tools of choice with no problems except as described in the question.
pyodbc is not actually a driver and doesn't contain one, its a 'module for ODBC databases', so it's more of an interface from python to ODBC driver to some database. That's why to use it you have to have an actual separate driver to connect to. Azure SQL being owned by Microsoft would reasonably require Microsoft's ODBC driver, while Postgres will require a Postgres ODBC driver, etc...
The ODBC driver manager is platform-specific, while the ODBC driver is database-specific. That would explain why if you are you are changing platforms or databases, you need to change drivers.
As Adrian noted, you don't need ODBC drivers for postgres, it is more common to use postgres/python drivers (eg: https://wiki.postgresql.org/wiki/Python)
psycopg2 is an actual PostgresSQL driver. It serves as client from Python to postgres, no intermediary required. That's why you don't need to install anything else when you use it. I haven't used pg8000, but based on this list it's a driver too, so you wan't need anything else.
EDITED TO ADD:
Think of a database as some 'black box' you need to activate, and its drivers as electrical sockets. ODBC driver is a specific type of socket (ODBC is a standard developed by Microsoft). If you are using ODBC plug from python (like pyodbc) to a database, you need to make sure the database has an ODBC socket installed/activated.
But your database can have other sockets too, like python-compatible DBAPI that's available on postgres. In that case you use a different direct DBAPI connector, like psycopg2.
Drivers are specific to a database. ODBC is a two stage process. There is the ODBC driver manager and then there are the database specific drivers that allow you to talk to a database. You don't need ODBC to connect to a Postgresql server. If you are going through Python you just need one of the Postgres drivers. You have already found pg8000. My preference is psycopg2.
I'm trying to set up my embedded Linux machine as a MySQL client, in order to connect to a external MySQL server (running on a remote machine). sqlite is not an option.
I understand, thanks to Basile Starynkevitch that I have to use libmysqlclient (because that is the only library to run such a connection and dealing with the MySQL client/server protocol on the client side).
Qt stats that:
You need the MySQL header files and as well as the shared library
libmysqlclient.so. Depending on your Linux distribution you may need
to install a package which is usually called "mysql-devel".
Did someone did this and can point out to the right package?
Yes, assuming what you want to do is use the QtSql API to access a MySQL database without connecting to an external MySQL server. With the embedded server library, the server runs in the same process as your client Qt Application, similar to how SQLite works.
One caveat though: the libmysqld embedded server library is deprecated as of MySQL 5.7.17 and will be removed in MySQL 8.0. (as mentionned on http://dev.mysql.com/doc/refman/5.7/en/libmysqld.html)
Your question is confusing and seems contradictory.
Either you want to work with an external MySQL server, and that means that your application opens a (tcp(7) socket) connection to some remote machine running mysqld. Then you have to use libmysqlclient (because that is the only library to run such a connection and dealing with the MySQL client/server protocol on the client side).
If that mysqld server is running as a different process on the same embedded Linux system you should have some way to start it (probably as part of the init scripts on it). Then you still use a socket communication to it, and you still need libmysqlclient. A possible difference with a remote machine running mysqld might be (but I am not sure) the socket family. Perhaps libmysqlclient is using unix(7) sockets in the special case of connecting to a server on the same machine.
Or you don't want any external server. You might consider libmysqld but as Romain answered it is deprecated and is becoming unsupported (so I feel that would be a very bad choice). Then all the database code is running on your embedded Linux computer, which also has all the data storage. In that case (relational database & data & storage on the same embedded Linux computer), I would recommend using sqlite instead because it is well supported and quite stable.
If your mysqld daemon is running on a remote machine you cannot (realistically) avoid libmysqlclient (otherwise you'll need to rewrite most of it).
I ended up doing the following:
Installing MySQL on my embedded Linux and tested it with
mysql --host=1.2.3.4 --user=Foo --password=FooPass testdb
When an MySQL server is runing on 1.2.3.4.
I recompiled Qt with the -sql-mysql option, so the new compiled version will include Qt MySQL plugin.
Test if Qt MySQL plugin is supported with the next code:
QStringList driverslist = QSqlDatabase::drivers();
QString str;
foreach (str, driverslist) { qDebug() << str }
Expected output is:
QMYSQL3
QMYSQL
Test that driver loaded as expected with the next code:
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("1.2.3.4");
db.setDatabaseName("TestDB");
db.setUserName("Foo");
db.setPassword("FooPass");
bool ok = db.open();
if(ok)
{
// "Connected"
}
I am currently on a project where I have 2 VM (virtual machine), a Windows and Linux one.
I also have an Oracle database where I have a simple table called "Material".
On the 2 VM, I want to connect to my Oracle database without any client or libraries. The thing is I want to create a script which would run on the VM and can connect to my database and insert some datas to my table "Material" but I can't install anything on my VM (like the mysqlclient for exemple).
So is it possible to connect to a database without installing anything on my VM? Or perhaps can I access to an online client to send my SQL to my Oracle Database?
I know it's quite difficult to understand my problem so if you have any question, feel free to ask.
I have Sybase installed on my Linux box (to which I have "root" access). However I do not have the access details to Sybase, is there any way I can find the port Sybase is listening on, and also use linux root user to connect to the database.
You should check sybase interface file at the first.
Read f.e. this article about interface file structure.
http://www.outlands.demon.co.uk/sybase/index.html
After that copy env. variables from sybase user bash profile ant try to connect to database with isql utility (also explained in this article).