问题
I'm trying to get the COLLECT function to work for me. I'm using 10g and therefore found that LISTAGG and WM_CONCAT will not work (invalid identifier errors). The data I have is for example as follows.
Order Lot
123 A23088
123 A23089
089 AABBCC
305 120848
305 CCDDYY
What I need returned is as follows
Order Lot
123 A23088, A23089
089 AABBCC
305 120848, CCDDYY
Using the following, I get the error: TO_STRING is an invalid identifier
TO_STRING ( CAST(COLLECT(DISTINCT LOT) AS varchar2(100)) ) AS LOT
Using the following, I get the error: expected CHAR "inconsistent datatypes: expected %s got %s"
TO_CHAR ( CAST(COLLECT(DISTINCT LOT) AS varchar2(100)) ) AS LOT
Using the following, I get the error: expected NUMBER "inconsistent datatypes: expected %s got %s"
COLLECT(DISTINCT WHSE_LOT)
Is there any way to get this function to work for me?
回答1:
The collect function creates a nested table, in your case a table of strings, which you would then cast to a specific type - that is, a type defined as a table of varchar2. You can't cast to a single string.
There are some well-known lists of string aggregation techniques, like this one. There is one that uses collect, but you still need the table type and a function to convert the generated table to a delimited string.
Copying that example verbatim:
CREATE OR REPLACE TYPE t_varchar2_tab AS TABLE OF VARCHAR2(4000);
/
CREATE OR REPLACE FUNCTION tab_to_string (p_varchar2_tab IN t_varchar2_tab,
p_delimiter IN VARCHAR2 DEFAULT ',') RETURN VARCHAR2 IS
l_string VARCHAR2(32767);
BEGIN
FOR i IN p_varchar2_tab.FIRST .. p_varchar2_tab.LAST LOOP
IF i != p_varchar2_tab.FIRST THEN
l_string := l_string || p_delimiter;
END IF;
l_string := l_string || p_varchar2_tab(i);
END LOOP;
RETURN l_string;
END tab_to_string;
/
With that type and function you then do:
SELECT tab_to_string(CAST(COLLECT(DISTINCT lot) AS t_varchar2_tab)) AS lot FROM ...
Interestingly, the 10g version of collect doesn't support DISTINCT
; it doesn't complain (!?), but leaves duplicates.
You can pass the collection through the set function to remove the duplicates:
SELECT tab_to_string(SET(CAST(COLLECT(DISTINCT lot) AS t_varchar2_tab))) AS lot FROM ...
Quick demo run in 10.2.0.5:
create table table1(order_no number, lot varchar2(10));
insert into table1 values (590288, '2016538');
insert into table1 values (590288, '2016535');
insert into table1 values (590288, '6016535');
insert into table1 values (590288, '2016535');
insert into table1 values (590288, '2016538');
SELECT order_no, tab_to_string(SET(CAST(COLLECT(DISTINCT lot) AS t_varchar2_tab))) AS LOT
FROM table1 WHERE order_no = 590288 GROUP BY order_no;
ORDER_NO LOT
---------- --------------------------------------------------
590288 2016538,2016535,6016535
来源:https://stackoverflow.com/questions/37423515/how-to-use-collect-with-varchar2-oracle-10g