Query on merge syntax

Question

There is a syntax I don't understand in this procedure.
what is the :1) trip stands for in the bottom of the proc? notice it is for a trip_sec_num col in the table.
create or replace PROCEDURE "myProc" IS
count INT;
QRY_count INT;
today DATE;
trip NUMBER;
BEGIN
EXECUTE IMMEDIATE 'CREATE GLOBAL TEMPORARY TABLE temp_left
ON COMMIT PRESERVE ROWS
AS SELECT *
FROM personPEV
WHERE a <> ''666''
AND b IS NOT NULL ';
EXECUTE IMMEDIATE 'MERGE INTO hugetbl
USING (SELECT da_boy.c1,
da_boy.c2,
da_boy.IN_OUT_CODE
FROM da_parent
LEFT OUTER JOIN temp_left da_boy
ON da_parent.c1 = da_boy.c1
AND da_parent.c2 = da_boy.c2
WHEN NOT MATCHED THEN
INSERT (c1
c2,
IN_OUT_CODE,
trip_SEQ_NUM) <-???
VALUES (
temp_left.c1,
temp_left.c2,
temp_left.IN_OUT_CODE,
:1)' USING trip; <-???

Answer 1

This "using syntax" is part of "EXECUTE IMMEDIATE". Look at the :1 in you merge statement. The value of this bind variable will be assigned same as trip.
Here is some example of USING syntax. Please consult oracle documentation for more.
SQL> ed
Wrote file afiedt.buf
  1  declare
  2  procedure p1 (p_empno emp.empno%type) IS
  3  v_name emp.ename%type;
  4  begin
  5  execute immediate 'SELECT ename from emp
  6  where empno=:1' INTO v_name using p_empno;
  7  dbms_output.put_line(v_name);
  8  end;
  9  begin
10  p1(7788);
11* end;
SQL> /
SCOTT
PL/SQL procedure successfully completed.By the way, it looks like that there is not much need to use dynamic SQL in your procedure, So Please consider it for rewriting. Unnecessary use of dynamic SQL is considered as bad practice.