Combine tables with common data - union

Question

Hi,
sorry if this has already been posted but I couldn't find a similar thread out there.
I have two small tables where there are duplicate parts. I'd like to combine the two into 1.
Table 1
Part_Num
Serialized_Part
Table 2
Part_Num
Hazardous_Part
a part can be both serialized and hazardous. I'd like to simply create a table
Final Table
Part_Num - distinct value combining tables.
Serialized_Part - value from table 1
Hazardous_Part - value from table 2
My SQL needs some work.
Thanks in advance,
--TD                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

Answer 1

Hi,
Welcome to the forum!
Whenever you have a question, it helps if you post a little sample data in a form people can use, for example:
CREATE TABLE     Table_1
(     Part_Num     NUMBER (6)     PRIMARY KEY
,     Serialized_Part     VARCHAR2 (10)
INSERT INTO table_1 (part_num, serialized_part) VALUES (1,  'Widget');
INSERT INTO table_1 (part_num, serialized_part) VALUES (2,  'Fubar');
CREATE TABLE     Table_2
(     Part_Num     NUMBER (6)     PRIMARY KEY
,     Hazardous_Part     VARCHAR2 (12)
INSERT INTO table_2 (part_num, hazardous_part) VALUES (2,  'Acid');
INSERT INTO table_2 (part_num, hazardous_part) VALUES (3,  'Knife');
CREATE TABLE     Final_Table
(     Part_Num     NUMBER (6)     PRIMARY KEY
,     Serialized_Part     VARCHAR2 (10)
,     Hazardous_Part     VARCHAR2 (12)
);Also post the results you want from that data. In this case, I think you want final_table, which starts with no rows, to contain this data when everything is finished:
. PART_NUM SERIALIZED HAZARDOUS_PA
         1 Widget
         2 Fubar      Acid
         3            KnifeHere's one way to get those results:
INSERT INTO     final_table (part_num, serialized_part, hazardous_part)
WITH     combined_data     AS
     SELECT     part_num
     ,     serialized_part
     ,     NULL     AS hazardous_part
     FROM     table_1
     UNION
     SELECT     part_num
     ,     NULL     AS serialized_part
     ,     hazardous_part
     FROM     table_2
SELECT       part_num
,       MIN (serialized_part)     AS serialized_part
,       MIN (hazardous_part)     AS hazardous_part
FROM       combined_data
GROUP BY  part_num
;You had the right idea with UNION, but UNION may leave two rows with the same part_num. GROUP BY can combine any number of rows into one. Since, at most, one those rows will have a serialized_part, and, likewise, at most one of those rows will have a hazardous_part, then it doesn't matter if you use MIN or MAX to get that one value.