Oracle INSTR replacement in SQLite

Actually, SQLite does support an INSTR function. But, it does not have a third parameter, which means, it always searches from the very beginning of the string.

But, we can workaround this by passing a substring to INSTR, and then offsetting the position found by adding the amount of the offset of the substring.

So, as an example, Oracle's call:

INSTR('catsondogsonhats', 'on', 7)

which would return 11, would become:

INSTR(SUBSTR('catsondogsonhats', 7), 'on') + 6

SQL

   CASE WHEN position = 0
        THEN INSTR(string, substring)
        WHEN position > 0
        THEN INSTR(SUBSTR(string, position), substring) + position - 1
        WHEN position < 0
        THEN LENGTH(RTRIM(REPLACE(string,
                                  substring,
                                  REPLACE(HEX(ZEROBLOB(LENGTH(substring))),
                                          '00',
                                          '¬')),
                          string)) - LENGTH(substring) + 1
   END

It assumes the ¬ character won't be part of the search string (but in the unlikely event this assumption is false could of course be changed to a different rarely used character).

SQLFiddle Demo

Some worked examples here: http://sqlfiddle.com/#!5/7e40f9/5

Credits

1. The positive position method was adapted from Tim Biegeleisen's answer. (But a zero value needs to be handled separately).
2. The negative position method used the method described in this question as a starting point.
3. The creation of a string consisting of a character repeated n times was taken from this simplified answer.