SubQuery

Hi!

I am using MyTable to serve the "next number"
functionality like PGSQL embeded "sequence" offers.
The only difference of the two is MyTable has 2 more
fields - "ID" and "Starting Effective Date".

The UPDATE SQL fails when I am trying to update
record

ID1 | 2001-08-01 | 11

to

ID1 | 2001-08-01 | 12

What mistake have I made?

CN
=================================
database1=# select * from mytable;
id | effectivedate | nextnumber
-----+---------------+------------
ID1 | 2001-06-01 | 10
ID1 | 2001-07-01 | 3
ID1 | 2001-08-01 | 11
ID2 | 2001-09-01 | 35
(4 rows)

database1=# SELECT EffectiveDate,NextNumber FROM
mytable s1
database1-# WHERE id='ID1' AND EffectiveDate=
database1-# (SELECT MAX(EffectiveDate) FROM mytable
s2
database1(# WHERE s1.id=s2.id AND
s2.EffectiveDate<=CURRENT_DATE);
effectivedate | nextnumber
---------------+------------
2001-08-01 | 11
(1 row)

database1=# UPDATE mytable SET
NextNumber=NextNumber+1
database1-# WHERE id='ID1' AND EffectiveDate=
database1-# (SELECT MAX(s2.EffectiveDate) FROM
mytable s2
database1(# WHERE s2.id=id AND
s2.EffectiveDate<=CURRENT_DATE);
UPDATE 0
database1=# UPDATE mytable SET
NextNumber=NextNumber+1
database1-# WHERE id='ID2' AND EffectiveDate=
database1-# (SELECT MAX(s2.EffectiveDate) FROM
mytable s2
database1(# WHERE s2.id=id AND
s2.EffectiveDate<=CURRENT_DATE);
UPDATE 1
database1=# select * from mytable;
id | effectivedate | nextnumber
-----+---------------+------------
ID1 | 2001-06-01 | 10
ID1 | 2001-07-01 | 3
ID1 | 2001-08-01 | 11
ID2 | 2001-09-01 | 36
(4 rows)

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