Update an Oracle table using another ungrouped table - sql

Question

The scenario involves two tables with the following structures :
>table e1:
Id Name Addr
---------------------
1 Ramas
2 Sam
3 Musa
4 Sebi
>table e1_addr:
Id Addr Mod_Date
-----------------------
1 Gzb 10-05-2018
1 Dli 18-05-2018
2 Gzb 25-05-2018
2 Dli 22-05-2018
3 Gzb 09-05-2018
3 Dli 05-05-2018
4 Gzb 14-05-2018
4 Dli 24-05-2018
table e1 has 4 personnel with no updated addresses in address column.
table e_addr has updated address record for each id with mod_date column having the date the record was entered.
I need to update table e1 so that its addr column has the value from the e1_addr table with maximum mod_date.
On my part, I have tried to fetch addr from e1_addr table corresponding to the max(mod_date) but cannot achieve the desired result.
Desired output is as follows :
Final Table :
Id Name Addr
------------------
1 Ramas Dli
2 Sam Gzb
3 Musa Gzb
4 Sebi Dli
Any and all help would be apprecited.
Please inform if i should give in some more details.

Answer 1

You can do this with keep:
update e1
set addr = (select max(a.addr) keep (dense_rank first order by mod_date desc)
from ei_addr a
where e1.id = a.id
);
I would suggest that you not store the address in two places and simply fetch the latest address when you query the e1 table.

Answer 2

You can try this query to update Addr column.
windows function with ROW_NUMBER to get Rownumber is 1 on e1_addr,which mean MAX Mod_Date.
then update e1.addr.
UPDATE
(
SELECT t.addr as OLD,t2.addr as NEW
FROM e1 t
INNER JOIN
(
SELECT t2.*,ROW_NUMBER() OVER(PARTITION BY t2.ID ORDER BY t2.Mod_Date desc) rn
FROM e1_addr t2
) t2 on t.id = t2.id
where t2.rn = 1
) t
SET t.OLD = t.NEW
or another update query you can try subquery.
UPDATE e1 t1
SET t1.addr = (SELECT t2.addr
FROM
(
SELECT t2.*,ROW_NUMBER() OVER(PARTITION BY t2.ID ORDER BY t2.Mod_Date desc) rn
FROM e1_addr t2
) t2
WHERE t2.rn = 1 and t1.id = t2.id
)
sqlfiddle:http://sqlfiddle.com/#!4/e14f5/1

Answer 3

Couldn't resist, the MERGE syntax wasn't mentioned yet:
MERGE INTO e1 USING (SELECT ID, MAX(addr) KEEP (DENSE_RANK FIRST ORDER BY mod_date DESC) AS newest_addr
FROM e1_addr GROUP BY ID) q ON (e1.ID = q.ID)
WHEN MATCHED THEN UPDATE SET e1.addr = q.newest_addr;
This subquery selects the newest address for each id:
SELECT ID, MAX(addr) KEEP (DENSE_RANK FIRST ORDER BY mod_date DESC) AS newest_addr
FROM e1_addr GROUP BY ID;
ID newest_addr
1 Dli
2 Gzb
3 Gzb
4 Dli
... and MERGE looks up each id in the subquery, and if it finds a match, it updates the addr.
Some people love it, some hate it.

Answer 4

Try this out:
Step1: Take id and max date from address table
Step 2: Join on id and max date with the address table to get the address
Step 3 Join this table with my e1 table to get the final output
select p.*,q.addr
from
e1 p
left join
(
select a.id,b.addr
from
(select id,max(mod_date) as updated_date
from e1_addr
group by id ) a
left join
e1_addr b
on a.id = b.id and a.updated_date = b.mod_date
) q
on p.id = q.id;
Let me know in case of any concerns

Answer 5

Thank you everyone for all the answers and different ways you posted to solve the query while i found a much simpler way to do same after having a discussion with one of my juniors. I felt pity for myself.
update e1 a set a.addr=(select addr from e1_addr b
where mod_date= (select max(mod_date) from e1_addr
where id= a.id ));
Thanks for all the support guys!