SUBSTR and INSTR SQL Oracle

Question

I've started using SUBSTR and INSTR in Oracle but I got confused when I came across this.

SELECT PHONE, SUBSTR(PHONE, 1, INSTR(PHONE, '-') -1)
FROM DIRECTORY;

So I know SUBSTR cuts values off, and INSTR shows where the occurrence is but the example I've put above has confused me, because the result it 362. When my original value was 362-127-4285. How does that work?

Answer 1

INSTR(PHONE, '-') gives the index of - in the PHONE column, in your case 4
and then SUBSTR(PHONE, 1, 4 - 1) or SUBSTR(PHONE, 1, 3)
gives the substring of the PHONE column from the 1st that has length of 3 chars which is 362,
if the value PHONE column is 362-127-4285.