create table t(description varchar2(12) primary key, 
  numbers varchar2(4000));
insert into t(description, numbers) values ('PRIME','2,3,5,7');
insert into t(description, numbers) values ('ODD','1,3,5,7,9');
commit;

Now I want to unpivot numbers in rows

select description,(column_value).getnumberval()  
from t,xmltable(numbers)

It is that simple

Works also with strings :

select (column_value).getstringval() 
from xmltable('"a","b","c"');

Compatibility: none. the protocol is completly different. Multiple graphical clients however do support both mode. But the basic “ftp” client will not work with sftp.

Ascii mode: only in ftp. In sftp, it is always binary so there will be no conversion. Also no blocksize, recordlength or primary/secondary space for your OS/390 connections.

Interactive mode: similar. you enter your username and password, do cd, put and get. But to quit, by will not work in sftp Use quit or exit instead

Batch mode: different. Most probably you will end up setting a private/public key infrastructure for your ssh connection and use scp (secure copy). If you are using a ssh client like putty, it is possible to do something like pscp -l user -pw password server:file .

Security: sftp is secure, ftp is not.

Speed: ftp is fast, sftp is slow !

Oh NOOOOOOO!!!!! What’s the point is bringing something new if it is slower !!!

Ok, let’s try to download a 100m file:

$ time (echo "open dbsrv01
user oracle secret
bin
get 100m"|ftp -n )

real    0m24.673s
user    0m0.030s
sys     0m0.016s
$ time scp -q oracle@dbsrv01:100m .

real    1m46.978s
user    0m0.108s
sys     0m0.202s

it is about 4x slower! Is there anything we could do about it?

Well, maybe :

$ time scp -q -o Compression=yes oracle@dbsrv01:100m .

real    0m18.634s
user    0m0.748s
sys     0m0.452s

ssh/scp/sftp have a compression mode. If you are transferring your large files across a slow network, this may be an interesting option to consider !

OpenSSH homepage : http://www.openssh.org

var n number
exec :n :=  9.9999999999999999999999999999999999e125
select to_number(to_char(:n)) from dual;
ORA-01722: invalid number

Why?
SQL Reference
If a positive NUMBER value is extremely large and cannot be represented in the specified format, then the infinity sign (~) replaces the value

select to_char(:n) from dual;
TO_CHAR(:N)
--------------
~

I wrote more about infinity here

SQL> insert into lsc_t(x) values(1);         ... (1) not committed
SQL> commit;                                 ... (1) committed

SQL> insert into lsc_t(x) values(2);         ... (2) not committed
SQL> alter table lsc_t disable primary key;  ... (2) committed

SQL> set autocommit ON
SQL> insert into lsc_t(x) values(3);         ... (3) committed
SQL> set autocommit OFF

SQL> insert into lsc_t(x) values(4);         ... (4) not committed
SQL> disc                                    ... (4) committed

Row 1 is committed after the commit keyword.

Row 2 is implicitely committed after before the alter table ddl statement.

Row 3 is autocommitted. Autocommit exists in sqlplus, but is more often seen in stateless applications (for instance a web application).

Row 4 is committed after a successfull disconnection.

But what appends if you kill your current session?

SQL> insert into lsc_t(x) values (5);

1 row created.

SQL> !ps
   PID TTY      TIME CMD
 13903 pts/33   0:00 ksh
 22384 pts/33   0:00 sqlplus

SQL> !kill 22384
Terminated

Ref: Overview of Transaction Management

A transaction ends when any of the following occurs:
- A user issues a COMMIT or ROLLBACK statement without a SAVEPOINT clause.
- A user runs a DDL statement such as CREATE, DROP, RENAME, or ALTER (*).
If the current transaction contains any DML statements, Oracle Database
first commits the transaction, and then runs and commits the DDL statement
as a new, single statement transaction.
- A user disconnects from Oracle Database. The current transaction is committed.
- A user process terminates abnormally. The current transaction is rolled back.

(*) but not ALTER SESSION …

I will try to rephrase it in a hierarchical way.

Let’s take all managers of Adams in EMP :

SELECT     empno, ename, mgr
      FROM emp
CONNECT BY NOCYCLE PRIOR mgr = empno
START WITH ename = 'ADAMS';
     EMPNO ENAME             MGR
---------- ---------- ----------
      7876 ADAMS            7788
      7788 SCOTT            7566
      7566 JONES            7839
      7839 KING                 

So far so good. Let’s imagine SCOTT has two managers, JONES and PAUL.

create table lsc_t AS
     (SELECT ename, empno, mgr
        FROM emp
      UNION ALL
      SELECT 'SCOTT', 7788, 9999
        FROM DUAL
      UNION ALL
      SELECT 'PAUL', 9999, NULL
        FROM DUAL);
SELECT     empno, ename, mgr
      FROM lsc_t
CONNECT BY NOCYCLE PRIOR mgr = empno
START WITH ename = 'ADAMS';
     EMPNO ENAME             MGR
---------- ---------- ----------
      7876 ADAMS            7788
      7788 SCOTT            7566
      7566 JONES            7839
      7839 KING                 
      7788 SCOTT            9999
      9999 PAUL                 

EMP is not supposed to allow this (primary key on empno), so I created a table LSC_T.

So far still fine, Paul is in my list of managers.

Let’s imagine Scott is the manager of Paul. In 9i and below, this would result in an ORA-0146 CONNECT BY loop in user data, but in 10g, and according to the doc The NOCYCLE parameter instructs Oracle Database to return rows from a query even if a CONNECT BY loop exists in the data.

Should I try ???

UPDATE lsc_t
   SET mgr = 7788
 WHERE ename = 'PAUL';
COMMIT ;
SELECT     empno, ename, mgr
      FROM lsc_t
CONNECT BY NOCYCLE PRIOR mgr = empno
START WITH ename = 'ADAMS';
     EMPNO ENAME             MGR
---------- ---------- ----------
      7876 ADAMS            7788
      7788 SCOTT            7566
      7566 JONES            7839
      7839 KING                 
      7788 SCOTT            9999

Due to a loop in user data, PAUL is no longer returned. I have no explanation so far.

Imagine that piece of code :

countlines() {
  c=$(sqlplus -s /nolog <<EOF | grep -v Connected
connect scott/tiger
set feed off head off
select count(*) from $1;
EOF
)
  echo there are $c lines in $1
}

countlines EMP
countlines DEPT

I can run this

time ./script1
there are 14 lines in EMP
there are 4 lines in DEPT

real    0m0.46s
user    0m0.06s
sys     0m0.09s

Sounds like a regular shell script. How could we optimize the countlines function? Well, we could create the connection only once and use coprocess pipe (with |& that is pipe ampersand)

sqlplus -s /nolog |&

print -p "connect scott/tiger"

read -p line
if [ $line != Connected. ]
then
  exit 1
fi

print -p "set feed off head off"

countlines() {
  print -p "select count(*) from $1;"
  read -p c
  echo "there is $c lines in $1"
}

countlines EMP
countlines DEPT

print -p disconnect

A two-ways pipe is opened with sqlplus. There is only one connect, and one disconnect.

Let’s check the performance :

$ time ./script2
there is 14 lines in EMP
there is 4 lines in DEPT

real    0m0.23s
user    0m0.00s
sys     0m0.01s

About twice as fast! Note the “Connected” output may not exist in recent version of sqlplus in silent mode. If you have a script that generates hundreds of connections, or which create a connection every 5 seconds or so, think about it

Enjoy your week-end

sqlldr control=x.ctl silent=header,feedback <<EOF
scott/tiger
EOF
Username:

The Username: prompt is displayed  

How do we get rid of this ?

sqlldr control=x.ctl silent=header,feedback <<EOF | grep -v "^Username:"
scott/tiger
EOF

There is no output. But what’s the error code

echo $?
1

The return code is 1

This is not the error code from sqlldr, but the error code from grep !

Ok, here is the trick, a bit cryptic if you are not familiar with file descriptors

( ( (sqlldr control=x <<EOF;echo $? >&3) |grep -v "^Username:" >&4 ) 3>&1 |(read x;exit $x) )4>&1
scott/tiger
EOF
echo $?
0

The return code is 0

ps -ef 
     UID   PID  PPID  C    STIME TTY      TIME CMD
lsc      13837 13825  0   May 11 pts/17   0:01 -ksh
oracle    4698  6294  0 12:00:40 ?        0:00 sqlplus -s system/manager
appluser  4229  4062  0 12:00:03 ?        0:00 sqlldr scott/tiger
applrun0 28445 28281  0 11:54:03 ?        0:00 imp king/gold full=y
...

What you see here above is definitely a security issue. For sqlplus, the trick is to use sqlplus /nolog and then pass connect system/manager as input or script.

For sqlldr (and exp/imp etc…), the trick is to use a parameter file.

To make it as safe as possible, the file must be unique, readable only for owner and removed after usage.

Ex:

umask 0077
TMPFILE=$(mktemp)
echo "userid=scott/tiger" >$TMPFILE
sqlldr parfile=$TMPFILE control=x.ctl silent=header,feedback
rm $TMPFILE

mktemp is an Unix utility that creates temp files with unique names.

I was just reading : http://www.mysql.com/products/enterprise/unlimited.html
Deploy an unlimited number of MySQL Enterprise Servers for the price of
a single CPU of Oracle Enterprise Edition
Today, there are over 5,000 organizations that spend more than $1Million on
License fees to Oracle, Microsoft, Sybase and IBM. In many cases, that’s money
that doesn’t need to be spent. Not only does open source save money, it
provides an architecture that is more scalable for modern web-based applications.
No wonder open source software has become a strategic initiative for CIOs & CFOs
in many organizations.

Clearly this need repositioning. (For Oracle, money need to be spent )

On the redundant offering MySQL and Oracle Database Express Edition, I could imagine Oracle will get rid of the free edition. Oracle seems to put effort on not releasing any database patch or security patch and the amount of features as well as the cpu/memory limitation are just way to annoying.

This is why I believe MySQL will survive XE.

Pure guess of course…

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.8.0 - 64bit Production
With the Partitioning option
JServer Release 9.2.0.8.0 - Production

SQL> drop table lsc_t ;

Table dropped.

SQL> create table lsc_t (x varchar2(255), y date);

Table created.

SQL> begin
  2    null;
  3  exception when others then
  4    insert into lsc_t (x,y)
  5          values (sqlerrm, sysdate);
  6  end;
  7  /

PL/SQL procedure successfully completed.

I was in the process of migrating a database with 10g and this piece of code became invalid

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> drop table lsc_t ;

Table dropped.

SQL> create table lsc_t (x varchar2(255), y date);

Table created.

SQL> begin
  2    null;
  3  exception when others then
  4    insert into lsc_t (x,y)
  5          values (sqlerrm, sysdate);
  6  end;
  7  /
        values (sqlerrm, sysdate);
                *
ERROR at line 5:
ORA-06550: line 5, column 17:
PL/SQL: ORA-00984: column not allowed here
ORA-06550: line 4, column 3:
PL/SQL: SQL Statement ignored

SQL> 

Ok, the code is wrong. It has been running for half a decade in production but the exception was never reached.

Note it is a bug, and putting sqlerrm after sysdate would have generate the exception even in 9i

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.8.0 - 64bit Production
With the Partitioning option
JServer Release 9.2.0.8.0 - Production

SQL> begin
  2    null;
  3  exception when others then
  4    insert into lsc_t (y,x)
  5          values (sysdate,sqlerrm);
  6  end;
  7  /
        values (sysdate,sqlerrm);
                        *
ERROR at line 5:
ORA-06550: line 5, column 25:
PL/SQL: ORA-00984: column not allowed here
ORA-06550: line 4, column 3:
PL/SQL: SQL Statement ignored

Just having fun with 10g migration