What is Sticky Bit?

If sticky bit is active, that file can be only deleted by root or owner.

to activate;
chmod +t file.txt
-rw-r--r-T
to unactivate;
chmod -t file.txt
-rw-r--r--

You may also want to read this entry;
http://ozsoyler.blogspot.com/2015/01/what-is-suid-and-guid.html

Useful shortcuts for vi editor

• vi myfile.txt
  to open file with vi editor
• vi + myfile.txt
  cursor goes to end of the file
• vi +200 myfile.txt
  cursor goes to 200th row
• :set list
  :set nolist
  see hidden characters or not
• :set number
  :set nonumber
  see number of lines or not
• :set paste
  activate paste option before get into insert mode (to resolve the commented lines problem)
• :set nopaste
  deactivate paste option before get into insert mode
• :[line_number]
  cursor goes to desired line
• l, k, h, j
  cursor goes to right, up, left, down
• w
  cursor goes to next word
• b
  cursor goes to start of the current word
• gg
  go top
• shift + g
  go bottom
• dd
  remove row
• p
  paste the clipboard data
• x
  remove one char
• yy
  copy the row
• u
  undo last operation
• o
  add new row
• :%d
  delete all lines
• /hello
  find "hello" word
  n
  go to next searched word
  N
  go to previous searched word

How to unlock database user account?

Please run the sql lines in SQL Editor as "sys" user;

SQL> ALTER USER "alper" ACCOUNT UNLOCK;

What are RAID levels 0/1/5/10?

Level	Minimum Disk Req.	Performance	Redundancy	Suggestions
0	2	Excellent	None	Not recommended for critical systems
1	2	Good	Excellent
5	3	Good	Good	Best cost effective option providing both performance and redundancy. Use this for DB that is heavily read oriented. Write operations will be slow.
10	4	Excellent	Excellent	If you can afford the dollar, this is the BEST option for any mission critical applications (especially databases).

Ref: http://www.thegeekstuff.com/2010/08/raid-levels-tutorial/

What is Oracle doing when you run commit?

The basic flow like that;

1. Oracle writes that "Commit has been executed" in related table from UNDO tablespace. 
2. SGA buffer cache - calling LGWR (Log Writer)
3. LGWR writes changed data (delta) to REDO log files
4. Tables' locks are released and marked as "TRANSACTION is completed" by Oracle

How to use Intersect function?

For instance, you want to see same jobs for employees that belong to different manager in employees table.

Please run the sql lines in SQL Editor as "hr" user;

SELECT job_id FROM employees
WHERE manager_id = 121
INTERSECT
SELECT job_id FROM employees
WHERE manager_id  = 122;

Used Database User: HR

Linux date function examples

e.g.
date -d now
date -d today
date -d yesterday
date -d mon
date -d tue
date -d wed
date -d thu
date -d fri
date -d sat
date -d sun
date --date="1 day ago"
date --date="1 week ago"
date --date="1 month ago"
date --date="1 year ago"
date -d "+10 days"
date -d "+10 weeks"
date -d "+10 months"
date -d "+10 years"

[CONCAT] How to merge two strings as a single string?

Please run the sql lines in SQL Editor as "hr" user;

e.g.
select CONCAT('Bilgi havuzu ','at ozsoyler.blogspot.com') from dual;
result
Bilgi havuzu at ozsoyler.blogspot.com

Used database user: hr
Used database server: oracle xe

[INITCAP] How to make uppercase the first character of each word in a string?

Please run the sql lines in SQL Editor as "hr" user;

e.g.
select INITCAP('ozsoyler.blogspot.com') from dual;
result
ozsoyler.Blogspot.Com

Used database user: hr
Used database server: oracle xe