how to substring string in oracle code example

Example 1: plsql left() function

SUBSTR( "20190601", 0, 6 )

Example 2: oracle right characters

-- For Oracle only

-- syntax 
SUBSTR(<main-string>,-<number-of-characters>)

-- example 
SUBSTR('Useless stuff',-9) -- OUTPUT: ess stuff

-- practical example
SELECT SUBSTR('Useless stuff',-9)
FROM DUAL;