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'