Re: [SQL] Typecasting datetype as date. How do I cope with NULLs?

Hello Stuart,

giovedì, 26 novembre 98, you wrote:

SR> Dear All,

SR> For those of you who don't want to wade through the details, here's the
SR> question: "How do I get the date portion of a datetime field for ALL
SR> ENTRIES in a table regardless of whether the entry is NULL or not? (N.B.
SR> Typecasting a datetime NULL as date generates an error)"

Table = a
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| dt | datetime | 8 |
| i | int4 | 4 |
+----------------------------------+----------------------------------+-------+

prova=> select * from a;
dt |i
----------------------+-
1998-12-26 16:35:23+01|1
1998-12-25 00:00:00+01|2
1998-12-27 00:00:00+01|3
(3 rows)

prova=> insert into a values (null,4);
INSERT 553697 1

prova=> select * from a;
dt |i
----------------------+-
1998-12-26 16:35:23+01|1
1998-12-25 00:00:00+01|2
1998-12-27 00:00:00+01|3
|4
(4 rows)

prova=> select *, extract(day from dt) from a;
dt |i|date_part
----------------------+-+---------
1998-12-26 16:35:23+01|1| 26
1998-12-25 00:00:00+01|2| 25
1998-12-27 00:00:00+01|3| 27
|4|
(4 rows)

-Jose'-