How to make select statement wait

Question

how can i make the select statement wait until there is not lock on the table( or a row) and return the row once the lock is released is there is a lock on it
example
i have a Table t1 with columns c1 and c2
process1
stmt1 as select c1 from t1 where c1=1
process2
select c1 from t1 where c1=1
/*some operations */
update t1 set c2=4 where c1=1
when process1 is executed it has to wait for process 2 to complete the return a row since it has to be synchronised and are run from different location
thanks in advance

Answer 1

You want to get around session consistent select. This is such a nice feature actually. But if you really want to do it, you can fool process 1 by telling it you want to do an update.
This is process 2:
SQL> update emp set sal=900 where empno=7369;
1 row updated.Note I do not commit yet.
This is process 1, with a "select for update".
SQL> select sal from emp where  empno=7369 for update wait 10;
select sal from emp where  empno=7369 for update wait 10
ERROR at line 1:
ORA-30006: resource busy; acquire with WAIT timeout expired"wait 10" tells Oracle to wait 10 seconds to get a lock.
Now process 2 commits within the 10 seconds. The result of process 1 is then:
SQL> select sal from emp where  empno=7369 for update wait 10;
       SAL
       900
SQL> commit;You have to issue a commit or rollback in process 1 immediately to release the lock that process 1 laid on the record.