Instr functions in Oracle

The instr syntax is as follows:
Instr (string1, string2 [, start_position [, nth_appearance])

Function Description:
This function returns the position of string2 in string1.

Start_positionThe parameter indicates the number of characters starting from string1 to find string2. This parameter is optional. If omitted, the default value is 1. The default search sequence of the instr function is from left to right. If this parameter is a negative number, search for it from the right.

Nth_appearanceReturns the position of string2 for the first time. This parameter is optional. If omitted, the default value is 1, that is, the first occurrence of string2 is returned.

Example:
Select instr ('ate floor ',' or ',-1, 1) "AAA" from dual;

Aaa
---------- Search from the right. The first occurrence of 'or' in the original string starts with 14th characters.
14