ELSIF V/S ELSE IF IN ORACLE

ELSIF does not need a matching END IF. If the condition for the 1st IF is not satisfied, then the ELSIF condition is checked.

ELSE IF will need a matching END IF, because a new IF block is started.

References:

PL/SQL Control Statements on Oracle® Database PL/SQL Language Reference

An IF statement in PL/SQL is structured as

IF <<some condition>>
THEN
  <<do something>>
ELSIF <<another condition>>
THEN
  <<do something else>>
ELSE
  <<do a third thing>>
END IF;

where both the ELSIF and the ELSE are optional. If you are seeing an ELSE IF, that indicates that someone is creating a nested IF statement (with a nested END IF) in an ELSE block. That is

IF <<some condition>>
THEN
  <<do something>>
ELSE
  IF <<another condition>>
  THEN
    <<do something else>>
  END IF;
END IF;

You can, if you so desire, nest PL/SQL blocks as deeply as you'd like. Generally, though, your code will be cleaner if you don't nest things more than necessary. Unless there is a compelling reason here to create a nested IF statement, you're much more likely to produce readable code using a single IF statement with one or more ELSIF blocks (or, even better, a CASE). Plus, that way you're not trying to count up all the END IF statements you need to close all the nested IF statements.