Re: Sub-query having NULL row returning FALSE result - Mailing list pgsql-general
| From | Sridhar N Bamandlapally |
|---|---|
| Subject | Re: Sub-query having NULL row returning FALSE result |
| Date | |
| Msg-id | CAGuFTBUXoq-9ibuCOu=oDr33k0v5ZtHzkn4SyKFKHsKQMVkJ7A@mail.gmail.com Whole thread Raw |
| In response to | Re: Sub-query having NULL row returning FALSE result ("David G. Johnston" <david.g.johnston@gmail.com>) |
| List | pgsql-general |
Hi
Just for info.
Actual query in Oracle (below)
----------------------------------
MERGE INTO relDocumentTypeMetaDataName t
USING (SELECT ? as DocumentTypeID, ? as DocumentContextID, ? as MetaDataNameID, ? as DocumentAbstractionIndexID FROM DUAL) s
ON (t.MetaDataNameID = s.MetaDataNameID AND t.DocumentTypeID = s.DocumentTypeID)
WHEN NOT MATCHED THEN
INSERT (DocumentTypeID, DocumentContextID, MetaDataNameID, FlatColumnNo) values
(s.DocumentTypeID, s.DocumentContextID, s.MetaDataNameID, (select nvl(max(FlatColumnNo), 0) + 1 FROM relDocumentTypeMetaDataName WHERE DocumentTypeID = ?));
Migrated query in PG (phase 1)
---------------------------------
WITH s AS (SELECT ? as DocumentTypeID, ? as DocumentContextID, ? as MetaDataNameID, ? as DocumentAbstractionIndexID)
INSERT INTO relDocumentTypeMetaDataName (DocumentTypeID, DocumentContextID, MetaDataNameID, FlatColumnNo, DocumentAbstractionIndexID)
SELECT s.DocumentTypeID, s.DocumentContextID, s.MetaDataNameID,
(SELECT coalesce(MAX(FlatColumnNo), 0) + 1 FROM relDocumentTypeMetaDataName WHERE DocumentTypeID = ?), s.DocumentAbstractionIndexID
FROM s WHERE s.DocumentTypeID NOT IN (SELECT DocumentTypeID FROM relDocumentTypeMetaDataName);
Migrated query in PG (phase 2) - after Tom Lane reply
--------------------------------------------------------
WITH s AS (SELECT ? as DocumentTypeID, ? as DocumentContextID, ? as MetaDataNameID, ? as DocumentAbstractionIndexID)
INSERT INTO relDocumentTypeMetaDataName (DocumentTypeID, DocumentContextID, MetaDataNameID, FlatColumnNo, DocumentAbstractionIndexID)
SELECT s.DocumentTypeID, s.DocumentContextID, s.MetaDataNameID,
(SELECT coalesce(MAX(FlatColumnNo), 0) + 1 FROM relDocumentTypeMetaDataName WHERE DocumentTypeID = ?), s.DocumentAbstractionIndexID
FROM s WHERE s.DocumentTypeID NOT IN (SELECT DocumentTypeID FROM relDocumentTypeMetaDataName WHERE DocumentTypeID IS NOT NULL);
Thanks
Sridhar
OpenText
On Wed, Jun 29, 2016 at 6:04 PM, David G. Johnston <david.g.johnston@gmail.com> wrote:
HiPlease go through below casepostgres=# CREATE TABLE emp (id INTEGER unique, ename VARCHAR);CREATE TABLEpostgres=# INSERT INTO emp VALUES (null, 'aaa');INSERT 0 1postgres=# INSERT INTO emp VALUES (null, 'bbb');INSERT 0 1postgres=# INSERT INTO emp VALUES (3, 'ccc');INSERT 0 1postgres=# INSERT INTO emp VALUES (4, 'ddd');INSERT 0 1postgres=# SELECT * FROM emp ;id | ename----+-------| aaa| bbb3 | ccc4 | ddd(4 rows)postgres=# SELECT * FROM (SELECT 5::integer id, 'eee'::varchar ename) nr;id | ename----+-------5 | eee(1 row)postgres=# INSERT INTO emp SELECT * FROM (SELECT 5::integer id, 'eee'::varchar ename) nr WHERE id NOT IN (SELECT id FROM emp);INSERT 0 0postgres=# SELECT * FROM emp ;id | ename----+-------| aaa| bbb3 | ccc4 | ddd(4 rows)postgres=#The application is generating SQL-Statement to avoid exception while insertingThe expected behavior is to INSERT row if the NEW id is not existing in table, but this is doing FALSEPlease advise me if am doing something wrong here or any alternateSubjectively, you are allowing an ID field to be NULL. That, for me, is wrong.Given this, as a follow-up to what Tom said, you need to decide what you wish to happen for your NULL IDs. Until you explain that behavior it is not possible to provide valid alternatives.Usually you want to use "EXISTS", not "IN"Oh, and try adding "WHERE id IS NOT NULL"David J.
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