CHR(0) in REGEXP_LIKE

Question

I am using the queries to check how chr(0) behaves in regexp_like.

CREATE TABLE t1(a char(10));
INSERT INTO t1 VALUES(\'0123456789\');
SELECT CASE WHEN REGE         


        

Answer 1

Aleksej kind of beat me to it, but CHR(0) is the value for the string terminator (kind of like the NULL keyword but not exactly). Think of it like an internal end-of-string indicator that CHR(0) apparently can see. Note that if you try the query with the keyword NULL, it will return zero, as nothing can be compared to NULL and the comparison thus will fail (as you were expecting). Interesting. Perhaps someone more experienced with the internal workings can explain further, I would be interested to hear more.