问题
Can you please help me converting the following Oracle MERGE
statement into a valid UPSERT
statement for use in a PostgreSQL 9.3 database?
MERGE INTO my_table a
USING (SELECT v_c1 key,
v_c2 AS pkey,
v_c3 AS wcount,
v_c4 AS dcount
FROM DUAL) b
ON ( a.key = b.key
AND a.pkey = b.pkey
WHEN MATCHED
THEN
UPDATE SET wcount = b.wcount,
dcount = b.dcount
WHEN NOT MATCHED
THEN
INSERT (key,
pkey,
wcount,
dcount)
VALUES(b.key,b.pkey,b.wcount,b.dcount);
回答1:
I don't think there's UPSERT statement in PostgreSQL 9.3, but you can do this:
with cte_dual as (
select
v_c1 as key,
v_c2 as pkey,
v_c3 as wcount,
v_c4 as dcount
), cte_update as (
update my_table as a set
wcount = b.wcount,
dcount = b.dcount
from cte_dual as b
where b.key = a.key and b.pkey = a.pkey
returning *
)
insert into my_table (key, pkey, wcount, dcount)
select d.key, d.pkey, d.wcount, d.dcount
from cte_dual as d
where not exists (select * from cte_update as u WHERE u.key = d.key and u.pkey = d.pkey)
You can read couple of similar questions:
- How to UPSERT (MERGE, INSERT ... ON DUPLICATE UPDATE) in PostgreSQL?
- Insert, on duplicate update in PostgreSQL?
回答2:
I ran on this today, read these, the docs, eventually used something very similar to what to my understanding the docs are advising now for UPSERT
:
INSERT INTO table (
$INSERT_COLUMN_NAMES
)
VALUES (
$INSERT_COLUMN_VALUES
)
ON CONFLICT (
$LIST_OF_PRIMARY_KEY_COLUMN_NAMES
)
DO UPDATE SET
$UPDATE_SET_SUBCLAUSE
WHERE
$WHERE_CONDITION_ON_PRIMARY_KEYS
;
I was actually working it at DAO level so I can not provide a meaningful example at the moment, will review this later.
If I'm not mistaken is working perfectly fine. I felt forced into create a primary key that wasn't there, but actually belonged there.
回答3:
upsert works in Postgres 9.3 ,
Example-
WITH upsert as
(update mytable2 m set sales=m.sales+d.sales, status=d.status from mytable d where m.pid=d.pid
RETURNING m.*
)
insert into mytable2 select a.pid, a.sales,'NEW' from mytable a where a.pid not in (select b.pid from mytable2 b);
来源:https://stackoverflow.com/questions/19395690/migrating-an-oracle-merge-statement-to-a-postgresql-upsert-statement