oracle substring

1-- ORACLE substr(string, start, [, length ])
2SELECT substr('Hello World', 4, 5) FROM DUAL;       -- lo Wo
3SELECT substr('Hello World', 4) FROM DUAL;          -- lo World
4SELECT substr('Hello World', -3) FROM DUAL;         -- rld
5SELECT substr('Hello World', -3, 2) FROM DUAL;      -- rl

1SUBSTR( "20190601", 0, 6 )

1SUBSTR( string, start_position [, length ] )

1-- For Oracle only
2
3-- syntax 
4SUBSTR(<main-string>,1,<number-of-characters>)
5
6-- example 
7SUBSTR('Useless stuff',1,10) -- OUTPUT: Useless st
8
9-- practical example
10SELECT SUBSTR('Useless stuff',1,10)
11FROM DUAL;

1-- For Oracle only
2
3-- syntax 
4SUBSTR(<main-string>,-<number-of-characters>)
5
6-- example 
7SUBSTR('Useless stuff',-9) -- OUTPUT: ess stuff
8
9-- practical example
10SELECT SUBSTR('Useless stuff',-9)
11FROM DUAL;

1SUBSTR(string, :START_POS, :SUBSTR_LENGTH);
2
3SELECT SUBSTR('ABCDEFG',3,4) FROM DUAL;
4--OUTPUT: CDEF