[GENERAL] Making NULLs visible.

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От Stuart Rison
Тема [GENERAL] Making NULLs visible.
Дата
Msg-id l03110727b2438933c9e6@[128.40.242.190]
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Ответы Re: [GENERAL] Making NULLs visible.  (Bruce Momjian <maillist@candle.pha.pa.us>)
Список pgsql-general
Dear All,

Is there a way to make postgreSQL 'show' nulls rather than have them appear
as blank fields?

e.g.

create table test (
    code    int2    primary key,
    name    text
);

insert into test (code,name) values (1234,'one two three four');
insert into test (code) values (5678);
insert into test (code,name) values (8888,NULL);
insert into test (code,name) values (9999,'');

now...

brecard5=> select * from test where name is null;
code|name
----+----
5678|
8888|
(2 rows)

brecard5=> select * from test;
code|name
----+------------------
1234|one two three four
5678|
9999|
8888|
(4 rows)

Question 1) How do I get postgres to do this:

select * from test;

code|name
----+------------------
1234|one two three four
5678|NULL
9999|
8888|NULL
?????

also, if I use the extended output option:

brecard5=> \x
turned on expanded table representation
brecard5=> select * from test where name is null;
Field| Value
-- RECORD 0 --
code| 5678
-- RECORD 1 --
code| 8888
(2 rows)

brecard5=> select * from test;
Field| Value
-- RECORD 0 --
code| 1234
name| one two three four
-- RECORD 1 --
code| 5678
-- RECORD 2 --
code| 9999
-- RECORD 3 --
code| 8888
(4 rows)

Again, how do I get visible NULLs?

Finally, as a somewhat unrelated set of questions:

2) In the extended output format, why is it that with 'select * from test',
RECORD 2 (code = 9999), the field name is not shown?  Afterall, the field
is not null, just empty (which I know shouldn't really happen in a well
designed db but...)?

3) How do I get the extended output to list ALL fields, irrespective of
whether they contain a value or are NULL?

thanks for your help,

Stuart.






+-------------------------+--------------------------------------+
| Stuart Rison            | Ludwig Institute for Cancer Research |
+-------------------------+ 91 Riding House Street               |
| Tel. (0171) 878 4041    | London, W1P 8BT, UNITED KINGDOM.     |
| Fax. (0171) 878 4040    | stuart@ludwig.ucl.ac.uk              |
+-------------------------+--------------------------------------+



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