Select Day count Excluding Saturday and Sunday for the Date range

SELECT
COUNT(DECODE(TO_CHAR(TO_DATE('Start Date','DD/MM/YYYY')+LEVEL-1,'D'),7,NULL,1,NULL,1)) FROM DUAL
CONNECT BY LEVEL <= TO_DATE('End Date','DD/MM/YYYY') -TO_DATE('Start Date','DD/MM/YYYY')+1;

Select Numbers without any Base Tables

SELECT LEVEL FROM DUAL CONNECT BY LEVEL <= 100

To_Char Funtion on Date

Translate Function

SELECT TRANSLATE('bernandas', 'abcdefghijklmnopqrstuvxyz', '0123456789qwertyuiop[kjhbv')
FROM DUAL;

Output
------
14ir0r30o


SELECT TRANSLATE('14ir0r30o', '0123456789qwertyuiop[kjhbv', 'abcdefghijklmnopqrstuvxyz')
FROM DUAL;

Output
------
bernandas

Occurance of a Letter in a String

SELECT LENGTH('BERNADNAS')-NVL(LENGTH(REPLACE('BERNADNAS','A')),0)
FROM DUAL