The error would be something like,
_X11TransSocketINETConnect() can't get address for local_host:6000: Hostname and service name not provided or found
This happens when you try to invoke a graphical UI via the command line or SSH. I have this for running DBCA and the installer of Oracle Client on Linux.
The solution is to run this application via a UI such as Gnome. You can do this by connecting to the machine using a remote UI login, such as via VNC.
Imagine the following table. First column (ID) is the Primary Key. There is a reflexive relationship between the 1st column and the 3rd (notice the colouring of the letters). Basically, Parent_ID mentions the parent of a particular ID in a hierarchical fashion representing a folder tree. So assuming this is in Oracle DB, how can we get the file path?
| ID | NAME | PARENT_ID |
| 1 | Root | 0 |
| 2 | First level Folder 1 | 1 |
| 3 | First level Folder 2 | 1 |
| 4 | Second level Folder | 2 |
There’s a neat little concept in Oracle to do this called CONNECT_BY. Lets look at the answer first,
SELECT path FROM (SELECT ID , PARENT_ID , FILE_NAME , SYS_CONNECT_BY_PATH(FILE_NAME, '/') AS path, RANK() OVER (ORDER BY SYS_CONNECT_BY_PATH(FILE_NAME, '/') DESC) AS rank FROM files WHERE id=? CONNECT BY PRIOR id = parent_id ) WHERE rank=1;The output for the above table is as follows,
| PATH |
| /Root/First level Folder 1/Second level Folder |
Now the explanation,
If more explanation is needed, please leave a comment and I shall get back to you
Well.. what I do code here is too simple for this blog but I’m pretty proud of my usage of generics in this.
Logic is, check for a value in the map… If it is there, get it. Otherwise, get a default.
Thats what this method do,
What if the Map’s values are Objects? Then I’d have to cast it to whatever type as well, right? Thats what this other method do
Consider a tree structure made up of Nodes and their specialized subclasses. Each Node has children which could be subclasses of Node.
We’re going to traverse this tree structure without using recursion but only using 2 Stacks.
Here goes the code:
I think the code is self explanatory.. Leave a comment if you bump into problems/improvements 
Problem:
Here’s the code
@Transactional
void outer(){
inner1(); // @Transactional
inner2(); // @Transactional
}
Both inner methods are transactional. Now, what I wanted to happen was, when outer() is called and if inner2() is rolled back, inner1() too should roll back.
Solution:
Use the NESTED option for the @Transactional annotation. As in the documentation, this is what happens when you do that,
Execute within a nested transaction if a current transaction exists, behave like PROPAGATION_REQUIRED else.
And PROPAGATION_REQUIRED or REQUIRED option means,
Support a current transaction, create a new one if none exists.
Based on that the code changes as follows,
@Transactional(propagation = Propagation.NESTED)
void outer(){
inner1(); // @Transactional
inner2(); // @Transactional
}
You can read about the other options in Spring Doc. I found another decent explanation here.
Since I couldn’t find a good list of extensions to CCK, I thought of making one
I am PRETTY sure I forgot some important ones. Please suggest those in the comments area. Thank you!!!
Problem: I had an SP to call which takes a param Date. I called this via JDBC with a valid Java Date, but it refused to save the time fields I supplied.
When preparing the SP for calling I did as follows,
mightySp('paramName',:paramName);
When supplying the parameter, I gave as follows,
tempPlsqlBlock.declareParameter(new SqlParameter("paramName", Types.DATE));
Solution: Instead of calling with param type Date, call with String and convert to date in the Java layer.
When preparing the SP for calling I used the TO_DATE method and convert the String to an Oracle Date as follows,
mightySp('paramName',TO_DATE(:paramName,'yyyy/mm/dd:hh:mi:ssam')
When supplying the parameter, I gave as follows,
tempPlsqlBlock.declareParameter(new SqlParameter("paramName", Types.VARCHAR));
The sessions in Oracle is shown in a system view called v$session. It has a quite a bit of columns, so my team mate Gowtham lists the most significant ones:
SELECT USERNAME, OSUSER, STATUS, MACHINE, PROGRAM, SERVER, TYPE, ACTION, CLIENT_INFO, LOGON_TIME, COMMAND, EVENT
FROM v$session
where USERNAME is not null
order by machine;
Just to summarise the list of all the events,
SELECT count(*), event FROM v$session s GROUP by event;
We can even filter them to find the locks and group them by name as follows,
SELECT osuser, event, count(*)
FROM v$session s
where event like 'enq:%'
GROUP by event,osuser
ORDER BY osuser;
A problem with Oracle DB that I see is that the ORDER BY clause is case sensitive. I came across this problem and I found the solution here in a post by Natalka Roshak. Solution is something like the following,
SELECT id,name FROM awesomeness WHERE order by nlssort(name,'NLS_SORT=BINARY_CI');
Here, she also mentions that this is valid for Oracle versions >= 10gR2.
In their documentation Oracle. says that it works by converting the string equivalent datatype to RAW format, which is then sorted and displayed.
They show interesting ways to use this function.
Anyhow, while I was sharing this with my team, one of my team mates, Gowtham, pointed out that this can be done by a more intuitive way: Simply convert everything to uppercase!
SELECT id,name FROM awesomeness WHERE order by UPPER(name);
My name is Gunith Devasurendra from the small Island Paradise known as Sri Lanka. I write programs for work and pleasure. I'm also an advocate of FOSS.
