oracle leftmost characters

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/*Using SUBSTR in Oracle (Example from hackerrank.com): */
2
3/*Simple select query...*/ 
4SELECT DISTINCT city 
5FROM station 
6
7/*Using WHERE and SUBSTR to find (distinct) cities in station table that begin 
8as well as end with a vowel.*/ 
9WHERE SUBSTR(city,1,1) IN ('A','E','I','O','U') 
10	AND substr(city,-1) IN ('a','e','i','o','u'); 
11
12/*Parameters for SUBSTR (Substring) in order are as follows: 
13String, Start, Length.*/