substr in oracle sql example

Example 1: plsql left() function

SUBSTR( "20190601", 0, 6 )

Example 2: oracle leftmost characters

-- For Oracle only

-- syntax 
SUBSTR(<main-string>,1,<number-of-characters>)

-- example 
SUBSTR('Useless stuff',1,10) -- OUTPUT: Useless st

-- practical example
SELECT SUBSTR('Useless stuff',1,10)
FROM DUAL;