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Chip
Guest
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 Posted: Tue May 03, 2005 8:13 pm Post subject: How can I get the size and precision of a field |
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Dear all,
I wrote a little quick test program trying to get the first field
information from a table. I can get the field name but the size and
precision are not. It just return an zero to me.
Here is the highlight of the code
type
edit1: TEdit;
edit2: TEdit;
edit3: TEdit;
MyQuery: TQuery;
procedure TFormMain.FormActive(Sender: Tobject);
begin
MyQuery.Active := False;
MyQuery.Close;
MyQuery.Sql.Clear;
MyQuery.Sql.Add('select * from table1');
MyQuery.Active := True;
// Get first field definition and display it
edit1.text := MyQuery.FieldDefList.FieldDefs[0].Name;
edit2.text := IntToStr(MyQuery.FieldDefList.FieldDefs[0].Size);
edit3.text := IntToStr(MyQuery.FieldDefList.FieldDefs[0].Precision;
end
Rgds,
Chip Ling
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Dan
Guest
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| Posted: Wed May 04, 2005 12:39 am Post subject: Re: How can I get the size and precision of a field |
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Chip,
It will help us a lot if you would tell us what database you are
using.
Dan
On 3 May 2005 13:13:14 -0700, "Chip" <chip_ling (AT) yahoo (DOT) ca> wrote:
| Quote: | Dear all,
I wrote a little quick test program trying to get the first field
information from a table. I can get the field name but the size and
precision are not. It just return an zero to me.
Here is the highlight of the code
type
edit1: TEdit;
edit2: TEdit;
edit3: TEdit;
MyQuery: TQuery;
procedure TFormMain.FormActive(Sender: Tobject);
begin
MyQuery.Active := False;
MyQuery.Close;
MyQuery.Sql.Clear;
MyQuery.Sql.Add('select * from table1');
MyQuery.Active := True;
// Get first field definition and display it
edit1.text := MyQuery.FieldDefList.FieldDefs[0].Name;
edit2.text := IntToStr(MyQuery.FieldDefList.FieldDefs[0].Size);
edit3.text := IntToStr(MyQuery.FieldDefList.FieldDefs[0].Precision;
end
Rgds,
Chip Ling
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Chip
Guest
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| Posted: Wed May 04, 2005 4:26 pm Post subject: Re: How can I get the size and precision of a field |
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Dan,
Good question. It is a propriertary database from IEX using the Simba
ODBC driver.
I re-test my code with Oracle database. Now I can get the field size
for the varchar field.
But all the numeric fields still return me zero on both Size and
Decision.
Rgds,
Chip
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Dan
Guest
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| Posted: Thu May 05, 2005 6:42 pm Post subject: Re: How can I get the size and precision of a field |
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On 4 May 2005 09:26:02 -0700, "Chip" <chip_ling (AT) yahoo (DOT) ca> wrote:
| Quote: | Dan,
Good question. It is a propriertary database from IEX using the Simba
ODBC driver.
I re-test my code with Oracle database. Now I can get the field size
for the varchar field.
But all the numeric fields still return me zero on both Size and
Decision.
This is not necessarily wrong. A Paradox number field for example: |
[from the help]
"The range of values possible for a number field is from -10^307 to
10^308 with 15 significant digits".
This means it is stored as a signed integer and a signed exponent.
There is no size or precision to set for this type of db. Maybe IEX
has a similar numeric field. I don't have the Oracle definitions handy
but I suspect it is similar to the Paradox type rather than the dBase
type.
HTH,
Dan
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Chip
Guest
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| Posted: Sat May 07, 2005 1:01 am Post subject: Re: How can I get the size and precision of a field |
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OK, I might be going the wrong way then.
Let's get back to the beginning. I want to get the field definition of
a table in Delphi. I can get the data type, field name. So far I don't
know how to get the size and precision of it.
I know how to do it in C++, just make the ODBC API calls and can get
all those field definition back. Pretty simple.
Does Delphi object has such a capability to get those information?
Rgds,
Chip
Dan wrote:
| Quote: | This is not necessarily wrong. A Paradox number field for example:
[from the help]
"The range of values possible for a number field is from -10^307 to
10^308 with 15 significant digits".
This means it is stored as a signed integer and a signed exponent.
There is no size or precision to set for this type of db. Maybe IEX
has a similar numeric field. I don't have the Oracle definitions
handy
but I suspect it is similar to the Paradox type rather than the dBase
type.
HTH,
Dan
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Dan
Guest
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| Posted: Sat May 07, 2005 2:32 am Post subject: Re: How can I get the size and precision of a field |
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On 6 May 2005 18:01:45 -0700, "Chip" <chip_ling (AT) yahoo (DOT) ca> wrote:
<snip>
| Quote: |
I know how to do it in C++, just make the ODBC API calls and can get
all those field definition back. Pretty simple.
You should be able to do exactly the same thing in Delphi. You might |
have to change a datatype here or there. For example, here is a BDE
API call I use successfully:
function Tdm.datapath: string;
var
dbDes: DBDesc; // DBDesc is defined in BDE unit
begin
try
Check(DbiGetDatabaseDesc(pchar('DCLSdata'), @dbDes));
// get Data path from BDE alias
result := dbDes.szPhyName;
except
result := 'C:Program Files ...
end;
end;
This uses Pchar(stringvalue) to cast the variable into the datatype
that the API uses.
hth,
Dan
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