[sql] PLS-00103: Encountered the symbol when expecting one of the following:

It seems ok but am getting exception please correct me.

declare
    var_number number;

begin
    var_number := 10;

    if var_number > 100 then
        dbms_output.put_line(var_number||' is greater than 100');
    elseif var_number < 100 then
        dbms_output.put_line(var_number||' is less than 100');
    else
        dbms_output.put_line(var_number||' is equal to 100');
    end if;

end;

Exception :

ORA-06550: line 8, column 8:
PLS-00103: Encountered the symbol "VAR_NUMBER" when expecting one of the following:
    := . ( @ % ;
ORA-06550: line 13, column 4:
PLS-00103: Encountered the symbol ";" when expecting one of the following:
    if

begin
    var_number := 10;

    if var_number > 100 then
        dbms_output.put_line(var_number||' is greater than 100');
    else if var_number < 100 then
        dbms_output.put_line(var_number||' is less than 100');
    else
        dbms_output.put_line(var_number||' is equal to 100');
    end if;
end if;

The IF statement has these forms in PL/SQL:

IF THEN

IF THEN ELSE

IF THEN ELSIF

You have used elseif which in terms of PL/SQL is wrong. That need to be replaced with ELSIF.

DECLARE
  mark NUMBER :=50;
BEGIN
  mark :=& mark;
  IF (mark BETWEEN 85 AND 100) THEN
    dbms_output.put_line('mark is A ');
  elsif (mark BETWEEN 50 AND 65) THEN
    dbms_output.put_line('mark is D ');
  elsif (mark BETWEEN 66 AND 75) THEN
    dbms_output.put_line('mark is C ');
  elsif (mark BETWEEN 76 AND 84) THEN
    dbms_output.put_line('mark is B');
  ELSE
    dbms_output.put_line('mark is F');
  END IF;
END;
/

The IF statement has these forms in PL/SQL:

IF THEN
IF THEN ELSE
IF THEN ELSIF

You have used elseif which in terms of PL/SQL is wrong. That need to be replaced with ELSIF.

So your code should appear like this.

    declare
        var_number number;
    begin
        var_number := 10;
        if var_number > 100 then
           dbms_output.put_line(var_number ||' is greater than 100');
--elseif should be replaced with elsif
        elsif var_number < 100 then
           dbms_output.put_line(var_number ||' is less than 100');
        else
           dbms_output.put_line(var_number ||' is equal to 100');
        end if;
    end; 

The problem is that the else and if are two operators here. Since you open a new 'if' you need a corresponding 'end if'.

Thus:

declare
mark number :=50;
begin
  mark :=& mark;
  if (mark between 85 and 100) then
    dbms_output.put_line('mark is A ');
  else 
    if (mark between 50 and 65) then
      dbms_output.put_line('mark is D ');
    else 
      if (mark between 66 and 75) then
        dbms_output.put_line('mark is C ');
      else 
        if (mark between 76 and 84) then
          dbms_output.put_line('mark is B');
        else 
          dbms_output.put_line('mark is F');
        end if;
      end if;
    end if;
  end if;
end;
/

Alternatively you can use elsif:

declare
mark number :=50;
begin
  mark :=& mark;
  if (mark between 85 and 100)
    then
    dbms_output.put_line('mark is A ');
  elsif (mark between 50 and 65) then
    dbms_output.put_line('mark is D ');
  elsif (mark between 66 and 75) then
    dbms_output.put_line('mark is C ');
  elsif (mark between 76 and 84) then
    dbms_output.put_line('mark is B');
  else 
    dbms_output.put_line('mark is F');
  end if;
end;
/