max() unexpected type conversion
| От | Hélder M. Vieira |
|---|---|
| Тема | max() unexpected type conversion |
| Дата | |
| Msg-id | 000901c5ee99$c275e380$580bfea9@hmv02 обсуждение исходный текст |
| Ответы |
Re: max() unexpected type conversion
|
| Список | pgsql-sql |
Hello.
I'm having some trouble with an unexpected conversion performed by the max()
function.
If max() operates on a 'varchar' type column, the result appears with 'text'
type.
Should I expect this behaviour in the current and later versions ?
I mention this because I'm using ODBC in VB, and this type conversion has a
bad outcome, because 'text' columns require a specific treatment (a second
reading of the column contents returns null). Therefore, if this conversion
is beeing made as a result of a design option, I'll have to use a different
approach (something like 'select ... order by ... desc limit 1').
A small sample follows, giving a 'text' type result:
create table test
( testcol varchar(4) not null
);
insert into test (testcol) values ('A');
insert into test (testcol) values ('A');
insert into test (testcol) values ('B');
insert into test (testcol) values ('B');
insert into test (testcol) values ('C');
insert into test (testcol) values ('C');
select max(testcol) from test;
Thank you
Hélder M. Vieira
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