INSTR( string1, string2 [, start_position [, nth_appearance ] ] )
 
-- string1 is the string to search.
 
-- string2 is the substring to search for in string1.
 
-- start_position is the position in string1 where the search 
-- will start. This argument is optional. If omitted, it defaults 
-- to 1. The first position in the string is 1. If the start_position 
-- is negative, the function counts back start_position number 
-- of characters from the end of string1 and then searches towards 
-- the beginning of string1.
 
-- nth_appearance is the nth appearance of string2. This is 
-- optional. If omitted, it defaults to 1.
 
-- Examples: 
INSTR('sqluniversity', 'i')  -- would return 6; the first occurrence of 'i'
INSTR('sqluniversity', 'i', 1, 1) -- would return 6; the first occurrence of 'i'
INSTR('sqluniversity', 'i', 1, 2) -- would return 11; the second occurrence of 'i'