PL/SQL: Selecting from a table into an assoc array

Question

I am trying to select data into a pl/sql associative array in one query. I know I can do this with a hardcoded key, but I wanted to see if there was some way I could reference another column (the key column) instead.

DECLARE
TYPE VarAssoc IS TABLE OF varchar2(2) INDEX BY varchar2(3);
vars VarAssoc;
BEGIN
SELECT foo, bar INTO vars(foo) FROM schema.table;
END;

I get an error saying foo must be declared when I do this. Is there some way to create my associate array in a single query or do I need to fall back on a FOR loop?

Answer 1

Just read your comment on APC's answer, it sounds like you figured this out on your own. But I figured I'd put the answer in anyway for future searchers.

This is simpler code, but does not have the speed advantage of using BULK COLLECT. Just loop through the rows returned by the query and set the elements in the associative array individually.

DECLARE
  TYPE VarAssoc IS TABLE OF varchar2(200) INDEX BY varchar2(30);
  vars VarAssoc;
BEGIN
  FOR r IN (SELECT table_name,tablespace_name FROM user_tables) LOOP
    vars(r.table_name) := r.tablespace_name;
  END LOOP;

  dbms_output.put_line( vars('JAVA$OPTIONS') );
END;

Answer 2

It would be neat if it were possible but that isn't a straightforward way of acheiving this.

What we can do is load the data into a regular PL/SQL collection and then load that into an associative array. Whethter this is faster than just looping round the table is a matter of tatse: it probably doesn't matter unless we're dealing with loads of data.

Given this test data ...

SQL> select * from t23
  2  order by c1
  3  /

C1 C2
-- ---
AA ABC
BB BED
CC CAR
DD DYE
EE EYE
ZZ ZOO

6 rows selected.

SQL>

...we can populate an associative array in two steps:

SQL> set serveroutput on
SQL>
SQL> declare
  2      type varassoc is table of varchar2(3) index by varchar2(2);
  3      vars varassoc;
  4
  5      type nt is table of t23%rowtype;
  6      loc_nt nt;
  7
  8  begin
  9      select * bulk collect into loc_nt from t23;
 10      dbms_output.put_line('no of recs = '||sql%rowcount);
 11
 12      for i in loc_nt.first()..loc_nt.last()
 13      loop
 14          vars(loc_nt(i).c1) := loc_nt(i).c2;
 15      end loop;
 16
 17      dbms_output.put_line('no of vars = '||vars.count());
 18
 19      dbms_output.put_line('ZZ = '||vars('ZZ'));
 20
 21  end;
 22  /
no of recs = 6
no of vars = 6
ZZ = ZOO

PL/SQL procedure successfully completed.

SQL>

The real question is probably whether populating an associative array performs better than just selecting rows in the table. Certainly if you have 11g Enterprise edition you should consider result set caching instead.