[HACKERS] NULL field records handling in order clause

PostgreSQL 6.1 , Linux RedHat 4.2 Kernel 2.0.30

Selecting all records and ordering ascending and descending on a field :

template1=> select * from pers order by cod;
             cod|nume  |salariu
- ----------------+------+-------
10              |Vasile|  45300
20              |Ion   | 192300
30              |Mihai |  92300
                |Fane  |
(4 rows)

template1=> select * from pers order by cod desc;
             cod|nume  |salariu
- ----------------+------+-------
30              |Mihai |  92300
20              |Ion   | 192300
10              |Vasile|  45300
                |Fane  |
(4 rows)


Record with nume='Fane' has NULL value in 'cod' field.

I think that ordering ascending the records on 'cod' field, records
having NULL values in 'cod' field should appear first. Should them ?


Other database information :

Database    = template1
 +------------------+----------------------------------+----------+
 |  Owner           |             Relation             |   Type   |
 +------------------+----------------------------------+----------+
 | postgres         | pers                             | table    |
 | postgres         | pers_cod                         | index    |
 +------------------+----------------------------------+----------+
template1=> \d pers

Table    = pers
+----------------------------------+----------------------------------+-------+
|              Field               |              Type                |
Length|
+----------------------------------+----------------------------------+-------+
| cod                              | (bp)char
|    16 |
| nume                             | varchar
|     0 |
| salariu                          | float8
|     8 |
+----------------------------------+----------------------------------+-------+
template1=>

'pers_cod' index is unique btree indexed on field cod.

Constantin Teodorescu
FLEX Consulting
Braila, ROMANIA
E-mail: teo@flex.ro

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