The Oracle PL/SQL INSTR function returns the location of a substring in a string.
The general format is:
INSTR(char1, char2 [,n [,m]])
n is an nonzero integer indicating the character of string where INSTR function begins the search. If position is negative, then INSTR counts backward from the end of string and then searches backward from the resulting position.
m is an integer indicating which occurrence of string INSTR function should search for. The value of occurrence must be positive.
Example 1:
SELECT INSTR('JOHN WILLIAMS','WILL') FROM DUAL;
returns:
6
Example 2:
SELECT INSTR('PEPE PEREZ','PE',1,2) FROM DUAL;
returns:
3