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

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.

Answer 3

are you absolutely married to associative arrays? And I assume that you are doing this because you want to be able to do a lookup against the array using a character key.
If so, have you considered implementing this as a collection type instead?
e.g.
CREATE OR REPLACE TYPE VAR_ASSOC as OBJECT(
KEYID VARCHAR2(3),
DATAVAL VARCHAR2(2)
)
/
CREATE OR REPLACE TYPE VAR_ASSOC_TBL AS TABLE OF VAR_ASSOC
/
CREATE OR REPLACE PROCEDURE USE_VAR_ASSOC_TBL
AS
vars Var_Assoc_tbl;
-- other variables...
BEGIN
select cast ( multiset (
select foo as keyid,
bar as dataval
from schema.table
) as var_Assoc_tbl
)
into vars
from dual;
-- and later, when you want to do your lookups
select ot.newfoo
,myvars.dataval
,ot.otherval
into ....
from schema.other_Table ot
join table(vars) as myvars
on ot.newfoo = myvars.keyid;
end;
/
This gives you the lookup by character key value and lets you do everything in bulk.