Update Query For ORACLE SQL DEVELOPER - sql

Question

I have four columns
id
fisrt_name
last_name
city
101
A
B
C
303
A
B
C
207
A
B
C
55
X
Y
Z
67
X
Y
Z
200
X
Y
Z
Basically FN, LN and city are same but the ids are different for these same values. I want to UPDATE the Ids of the duplicate rows as same, shown in table below using oracle sql developer. The id can be update to either of the three but it should become same for all the three duplicate rows.
id
fisrt_name
last_name
city
101
A
B
C
101
A
B
C
101
A
B
C
55
X
Y
Z
55
X
Y
Z
55
X
Y
Z
I tried this
UPDATE TABLE T1 SET
T1.ID = ID
WHERE ROWID IN (SELECT ROWID FROM(
SELECT ROWID,ROW_NUMBER() OVER(PARTITION BY ID, CITY ORDER BY ADR_LINE_1) AS RN, ID, CITY
FROM TABLE
WHERE (first_name,last_name,city) IN (first_name,last_name,city
from table
group by first_name,last_name,city
having count(distinct id) >= 2)) WHERE RN = 1);
It updates the desired rows but with the same ids not with what I want.

Answer 1

Here's one way - join your table to the result of an aggregate query and update (group by fn, ln, city, filter out the groups with a single id, and select min(id) in the remaining groups, then use that to update).
Set up the test case:
create table my_table (id, first_name, last_name, city) as
select 101, 'A', 'B', 'C' from dual union all
select 303, 'A', 'B', 'C' from dual union all
select 207, 'A', 'B', 'C' from dual union all
select 55, 'X', 'Y', 'Z' from dual union all
select 67, 'X', 'Y', 'Z' from dual union all
select 200, 'X', 'Y', 'Z' from dual union all
select 333, 'D', 'F', 'G' from dual
;
Table MY_TABLE created.
Update:
update
( select t.id, g.min_id
from my_table t
inner join
( select min(id) as min_id, first_name, last_name, city
from my_table
group by first_name, last_name, city
having min(id) != max(id)
) g
using (first_name, last_name, city)
)
set id = min_id
where id != min_id
;
4 rows updated.
Check the result:
select * from my_table;
ID FIRST_NAME LAST_NAME CITY
---------- ---------- ---------- ----------
101 A B C
101 A B C
101 A B C
55 X Y Z
55 X Y Z
55 X Y Z
333 D F G
NOTE: If ID may be null, that will require a bit of additional handling (but, the column should be NOT NULL.... is it?)

Answer 2

One option would be using MIN() Analytic Function with grouping by repeating three columns (first_name, last_name, city) through a MERGE Statement such as
MERGE INTO tab t1
USING ( SELECT MIN(id) OVER (PARTITION BY first_name, last_name, city) AS new_id
FROM tab t ) t2
ON ( t1.rowid = t2.rowid )
WHEN MATCHED THEN UPDATE SET t1.id = t2.new_id
Demo

Answer 3

I would go for a correlated subquery:
update t1
set id = (
select min(id)
from mytable t1
where t1.first_name = t.first_name and t1.lastname = t.lastname and t1.city = t.city
)
where id > (
select min(id)
from mytable t1
where t1.first_name = t.first_name and t1.lastname = t.lastname and t1.city = t.city
)
This query would take advantage of an index on (firstname, lastname, city, id) - although updating the rows will require updating the index too...