get percentages on SQL querry - Oracle

If we want to get the percentage of some column on same query, we can do it using "ratio_to_report() over()" function.

ratio_to_report(Number_of_books) over()

let's say we have following table called tbl_books.

Book	Number_of_books
Book1	30
Book1	20
Book1	10

if we want to get percentages of each book over total number of books we can do as following,

select book,ratio_to_report(Number_of_books) over() * 100 as percentage from tbl_books

it gives,

Book	percentage
Book1	50
Book1	33.333333333
Book1	16.66666666

Where does MySQL store data in PC

Windows

Find the my.ini file which store in the MySQL installation folder.

and then open the file and Find the “datadir”, this is the where does MySQL stored the data in Windows.

datadir="C:/ProgramData/MySQL/MySQL Server 5.5/Data/"

Linux

Find the my.cnf with the sudo find / -name my.cnf command.

2) viewthe my.cnf file cat /etc/mysql/my.cnf

yongmo@myserver:~$ cat /etc/mysql/my.cnf
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
# 
[mysqld]
#
# * Basic Settings
#
user   = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket  = /var/run/mysqld/mysqld.sock
port   = 3306
basedir  = /usr
datadir  = /var/lib/mysql
tmpdir  = /tmp
language = /usr/share/mysql/english
skip-external-locking

3) Find the “datadir”, this is where does MySQL stored the data in Linux system.