How do you specify IN clause in a dynamic query using a variable?

Question

In PL/SQL, you can specify the values for the IN operator using concatenation:

v_sql := \'select field1
from table1
where field2 in (\' || v_list || \')\';
<         


        

Answer 1

As per @Marcin's answer you can't do this, however, there's a fair bit to add to that, as your query should actually work, i.e. run.

Simply put, you cannot use a bind variable for a table or column. Not only that, bind variables they are assumed to be a character, so if you want a number you have to use to_number(:b1) etc.

This is where your query falls down. As you're passing in a string Oracle assumes that your entire list is a single string. Thus you are effectively running:

select field1
  from table1
where field2 = v_list

There is no reason why you can't do this a different way though. I'm going to assume you're dynamically creating v_list, which means that all you need to do is create this list differently. A series of or conditions is, purportedly :-), no different to using an in.

By purportedly, I mean never rely on something that's untested. Although Tom does say in the link that there may be performance constraints there's no guarantee that it wasn't quicker than using in to begin with. The best thing to do is to run the trace on your query and his and see what difference there is, if any.

SQL> set serveroutput on
SQL>
SQL> declare
  2
  3    l_string varchar2(32767);
  4    l_count number;
  5
  6  begin
  7
  8      for xx in ( select rownum as rnum, a.*
  9                    from user_tables a
 10                   where rownum < 20 ) loop
 11
 12        if xx.rnum = 1 then
 13          l_string := 'table_name = ''' || xx.table_name || '''';
 14        else
 15          l_string := l_string || ' or table_name = ''' || xx.table_name || '
''';
 16        end if;
 17
 18      end loop;
 19
 20      execute immediate 'select count(*)
 21                           from user_tables
 22                          where ' || l_string
 23                           into l_count
 24                                ;
 25
 26      dbms_output.put_line('count is ' || l_count);
 27
 28  end;
 29  /
count is 19

PL/SQL procedure successfully completed.