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  #31  
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Mark D Powell
 
Posts: n/a

Default Re: most idiomatic way to iterate over an associative array? - 05-10-2008 , 09:08 AM





On May 8, 2:02*pm, Urs Metzger <u... (AT) ursmetzger (DOT) de> wrote:
Quote:
Mark D Powell schrieb:



On May 7, 4:07 am, Robert Klemme <shortcut... (AT) googlemail (DOT) com> wrote:
On May 7, 6:51 am, m... (AT) pixar (DOT) com wrote:

This is what I'm doing now... is there a better way?
It would be great if there were some construct such
as 'for i in x begin ... end;'
* * i := x.first;
* * loop
* * * * dbms_output.put_line(i);
* * * * exit when i = x.last;
* * * * i := x.next(i);
* * end loop;
Many TIA!
Mark
This will break for empty collections. *You can do

SQL> set serverout on
SQL> DECLARE *TYPE population_type IS TABLE OF NUMBER INDEX BY
VARCHAR2(64);
* 2 * *continent_population population_type;
* 3 * *which VARCHAR2(64);
* 4 *BEGIN
* 5 * *dbms_output.put_line('-----------');
* 6
* 7 * *which := continent_population.FIRST;
* 8 * *while which is not null loop
* 9 * * *dbms_output.put_line(which || ' -> ' ||
continent_population(which));
*10 * * *which := continent_population.NEXT(which);
*11 * *end loop;
*12
*13 * *dbms_output.put_line('-----------');
*14
*15 * *continent_population('Australia') := 30000000;
*16 * *continent_population('Antarctica') := 1000; -- Creates new
entry
*17 * *continent_population('Antarctica') := 1001; -- Replaces
previous value
*18
*19 * *which := continent_population.FIRST;
*20 * *while which is not null loop
*21 * * *dbms_output.put_line(which || ' -> ' ||
continent_population(which));
*22 * * *which := continent_population.NEXT(which);
*23 * *end loop;
*24
*25 * *dbms_output.put_line('-----------');
*26 *END;
*27 */
-----------
-----------
Antarctica -> 1001
Australia -> 30000000
-----------

PL/SQL procedure successfully completed.

SQL

Cheers

robert

seehttp://download.oracle.com/docs/cd/B19306_01/appdev.102/b14261/collec......

I think I would consider the For I in 1..n construct

UT1 > l
* 1 *declare
* 2 *type t_array is table of varchar2(10) index by binary_integer;
* 3 *t_list * t_array;
* 4 *begin
* 5 *t_list(1) := 'one';
* 6 *t_list(2) := 'two';
* 7 *t_list(3) := 'three';
* 8 *t_list(4) := 'four';
* 9 *t_list(5) := 'five';
*10 *for I in 1..t_list.last loop
*11 * *dbms_output.put_line(t_list(I));
*12 *end loop;
*13* end;
UT1 > /
one
two
three
four
five

PL/SQL procedure successfully completed.

Again as Robert warned in his solution the array should not be empty.

HTH -- Mark D Powell --

Mark,

this will work if - and only if - your array has no gaps:

SQL> declare
* *2 * * type t_array is table of varchar2(10) index by binary_integer;
* *3 * * t_list * t_array;
* *4 *begin
* *5 * * t_list(1) := 'one';
* *6 * * t_list(2) := 'two';
* *7 * * -- t_list(3) := 'three';
* *8 * * t_list(4) := 'four';
* *9 * * t_list(5) := 'five';
* 10 * * for I in 1..t_list.last loop
* 11 * * * *dbms_output.put_line(t_list(I));
* 12 * * end loop;
* 13 *end;
* 14 */
one
two
declare
*
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at line 11

your approach won't work for arrays with index by varchar2.

The way to do is:

SQL> declare
* *2 * * type t_array is table of varchar2(10) index by binary_integer;
* *3 * * t_list * t_array;
* *4 * * i * * * *binary_integer;
* *5 *begin
* *6 * * t_list(1) := 'one';
* *7 * * t_list(2) := 'two';
* *8 * * t_list(4) := 'four';
* *9 * * t_list(50) := 'fifty';
* 10
* 11 * * i := t_list.first;
* 12 * * while i is not null loop
* 13 * * * *dbms_output.put_line(t_list(I));
* 14 * * * *i := t_list.next(i);
* 15 * * end loop;
* 16 *end;
* 17 */
one
two
four
fifty

This will also work with empty collections or varchar2 indexes.

Hth,
Urs Metzger- Hide quoted text -

- Show quoted text -
The recommendation to use table.next to move throught the array is an
excellent point whenever the array could be empty or have holes in
it. Most of the time the arrays I have worked with are populated
earlier in the code so there are never gaps between first and last.
Still one should always try to write code that will work in all
possible circumstances and not just with the data in front of you.

Thanks.
-- Mark D Powell --





Reply With Quote
  #32  
Old   
Mark D Powell
 
Posts: n/a

Default Re: most idiomatic way to iterate over an associative array? - 05-10-2008 , 09:08 AM





On May 8, 2:02*pm, Urs Metzger <u... (AT) ursmetzger (DOT) de> wrote:
Quote:
Mark D Powell schrieb:



On May 7, 4:07 am, Robert Klemme <shortcut... (AT) googlemail (DOT) com> wrote:
On May 7, 6:51 am, m... (AT) pixar (DOT) com wrote:

This is what I'm doing now... is there a better way?
It would be great if there were some construct such
as 'for i in x begin ... end;'
* * i := x.first;
* * loop
* * * * dbms_output.put_line(i);
* * * * exit when i = x.last;
* * * * i := x.next(i);
* * end loop;
Many TIA!
Mark
This will break for empty collections. *You can do

SQL> set serverout on
SQL> DECLARE *TYPE population_type IS TABLE OF NUMBER INDEX BY
VARCHAR2(64);
* 2 * *continent_population population_type;
* 3 * *which VARCHAR2(64);
* 4 *BEGIN
* 5 * *dbms_output.put_line('-----------');
* 6
* 7 * *which := continent_population.FIRST;
* 8 * *while which is not null loop
* 9 * * *dbms_output.put_line(which || ' -> ' ||
continent_population(which));
*10 * * *which := continent_population.NEXT(which);
*11 * *end loop;
*12
*13 * *dbms_output.put_line('-----------');
*14
*15 * *continent_population('Australia') := 30000000;
*16 * *continent_population('Antarctica') := 1000; -- Creates new
entry
*17 * *continent_population('Antarctica') := 1001; -- Replaces
previous value
*18
*19 * *which := continent_population.FIRST;
*20 * *while which is not null loop
*21 * * *dbms_output.put_line(which || ' -> ' ||
continent_population(which));
*22 * * *which := continent_population.NEXT(which);
*23 * *end loop;
*24
*25 * *dbms_output.put_line('-----------');
*26 *END;
*27 */
-----------
-----------
Antarctica -> 1001
Australia -> 30000000
-----------

PL/SQL procedure successfully completed.

SQL

Cheers

robert

seehttp://download.oracle.com/docs/cd/B19306_01/appdev.102/b14261/collec......

I think I would consider the For I in 1..n construct

UT1 > l
* 1 *declare
* 2 *type t_array is table of varchar2(10) index by binary_integer;
* 3 *t_list * t_array;
* 4 *begin
* 5 *t_list(1) := 'one';
* 6 *t_list(2) := 'two';
* 7 *t_list(3) := 'three';
* 8 *t_list(4) := 'four';
* 9 *t_list(5) := 'five';
*10 *for I in 1..t_list.last loop
*11 * *dbms_output.put_line(t_list(I));
*12 *end loop;
*13* end;
UT1 > /
one
two
three
four
five

PL/SQL procedure successfully completed.

Again as Robert warned in his solution the array should not be empty.

HTH -- Mark D Powell --

Mark,

this will work if - and only if - your array has no gaps:

SQL> declare
* *2 * * type t_array is table of varchar2(10) index by binary_integer;
* *3 * * t_list * t_array;
* *4 *begin
* *5 * * t_list(1) := 'one';
* *6 * * t_list(2) := 'two';
* *7 * * -- t_list(3) := 'three';
* *8 * * t_list(4) := 'four';
* *9 * * t_list(5) := 'five';
* 10 * * for I in 1..t_list.last loop
* 11 * * * *dbms_output.put_line(t_list(I));
* 12 * * end loop;
* 13 *end;
* 14 */
one
two
declare
*
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at line 11

your approach won't work for arrays with index by varchar2.

The way to do is:

SQL> declare
* *2 * * type t_array is table of varchar2(10) index by binary_integer;
* *3 * * t_list * t_array;
* *4 * * i * * * *binary_integer;
* *5 *begin
* *6 * * t_list(1) := 'one';
* *7 * * t_list(2) := 'two';
* *8 * * t_list(4) := 'four';
* *9 * * t_list(50) := 'fifty';
* 10
* 11 * * i := t_list.first;
* 12 * * while i is not null loop
* 13 * * * *dbms_output.put_line(t_list(I));
* 14 * * * *i := t_list.next(i);
* 15 * * end loop;
* 16 *end;
* 17 */
one
two
four
fifty

This will also work with empty collections or varchar2 indexes.

Hth,
Urs Metzger- Hide quoted text -

- Show quoted text -
The recommendation to use table.next to move throught the array is an
excellent point whenever the array could be empty or have holes in
it. Most of the time the arrays I have worked with are populated
earlier in the code so there are never gaps between first and last.
Still one should always try to write code that will work in all
possible circumstances and not just with the data in front of you.

Thanks.
-- Mark D Powell --





Reply With Quote
  #33  
Old   
Mark D Powell
 
Posts: n/a

Default Re: most idiomatic way to iterate over an associative array? - 05-10-2008 , 09:08 AM


On May 8, 2:02*pm, Urs Metzger <u... (AT) ursmetzger (DOT) de> wrote:
Quote:
Mark D Powell schrieb:



On May 7, 4:07 am, Robert Klemme <shortcut... (AT) googlemail (DOT) com> wrote:
On May 7, 6:51 am, m... (AT) pixar (DOT) com wrote:

This is what I'm doing now... is there a better way?
It would be great if there were some construct such
as 'for i in x begin ... end;'
* * i := x.first;
* * loop
* * * * dbms_output.put_line(i);
* * * * exit when i = x.last;
* * * * i := x.next(i);
* * end loop;
Many TIA!
Mark
This will break for empty collections. *You can do

SQL> set serverout on
SQL> DECLARE *TYPE population_type IS TABLE OF NUMBER INDEX BY
VARCHAR2(64);
* 2 * *continent_population population_type;
* 3 * *which VARCHAR2(64);
* 4 *BEGIN
* 5 * *dbms_output.put_line('-----------');
* 6
* 7 * *which := continent_population.FIRST;
* 8 * *while which is not null loop
* 9 * * *dbms_output.put_line(which || ' -> ' ||
continent_population(which));
*10 * * *which := continent_population.NEXT(which);
*11 * *end loop;
*12
*13 * *dbms_output.put_line('-----------');
*14
*15 * *continent_population('Australia') := 30000000;
*16 * *continent_population('Antarctica') := 1000; -- Creates new
entry
*17 * *continent_population('Antarctica') := 1001; -- Replaces
previous value
*18
*19 * *which := continent_population.FIRST;
*20 * *while which is not null loop
*21 * * *dbms_output.put_line(which || ' -> ' ||
continent_population(which));
*22 * * *which := continent_population.NEXT(which);
*23 * *end loop;
*24
*25 * *dbms_output.put_line('-----------');
*26 *END;
*27 */
-----------
-----------
Antarctica -> 1001
Australia -> 30000000
-----------

PL/SQL procedure successfully completed.

SQL

Cheers

robert

seehttp://download.oracle.com/docs/cd/B19306_01/appdev.102/b14261/collec......

I think I would consider the For I in 1..n construct

UT1 > l
* 1 *declare
* 2 *type t_array is table of varchar2(10) index by binary_integer;
* 3 *t_list * t_array;
* 4 *begin
* 5 *t_list(1) := 'one';
* 6 *t_list(2) := 'two';
* 7 *t_list(3) := 'three';
* 8 *t_list(4) := 'four';
* 9 *t_list(5) := 'five';
*10 *for I in 1..t_list.last loop
*11 * *dbms_output.put_line(t_list(I));
*12 *end loop;
*13* end;
UT1 > /
one
two
three
four
five

PL/SQL procedure successfully completed.

Again as Robert warned in his solution the array should not be empty.

HTH -- Mark D Powell --

Mark,

this will work if - and only if - your array has no gaps:

SQL> declare
* *2 * * type t_array is table of varchar2(10) index by binary_integer;
* *3 * * t_list * t_array;
* *4 *begin
* *5 * * t_list(1) := 'one';
* *6 * * t_list(2) := 'two';
* *7 * * -- t_list(3) := 'three';
* *8 * * t_list(4) := 'four';
* *9 * * t_list(5) := 'five';
* 10 * * for I in 1..t_list.last loop
* 11 * * * *dbms_output.put_line(t_list(I));
* 12 * * end loop;
* 13 *end;
* 14 */
one
two
declare
*
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at line 11

your approach won't work for arrays with index by varchar2.

The way to do is:

SQL> declare
* *2 * * type t_array is table of varchar2(10) index by binary_integer;
* *3 * * t_list * t_array;
* *4 * * i * * * *binary_integer;
* *5 *begin
* *6 * * t_list(1) := 'one';
* *7 * * t_list(2) := 'two';
* *8 * * t_list(4) := 'four';
* *9 * * t_list(50) := 'fifty';
* 10
* 11 * * i := t_list.first;
* 12 * * while i is not null loop
* 13 * * * *dbms_output.put_line(t_list(I));
* 14 * * * *i := t_list.next(i);
* 15 * * end loop;
* 16 *end;
* 17 */
one
two
four
fifty

This will also work with empty collections or varchar2 indexes.

Hth,
Urs Metzger- Hide quoted text -

- Show quoted text -
The recommendation to use table.next to move throught the array is an
excellent point whenever the array could be empty or have holes in
it. Most of the time the arrays I have worked with are populated
earlier in the code so there are never gaps between first and last.
Still one should always try to write code that will work in all
possible circumstances and not just with the data in front of you.

Thanks.
-- Mark D Powell --





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