[Lazarus] RE : How to get field-names of a table ?

[Ludo Brands]

> > When you open the query you object is deleted.
> > If yuo need only a field name is
> >
> > Query1.sql.text:= "select * from mytable";
> > Query1.open;
> > Name:=Query1.Fields[0].fieldname;
> >
> 
> Thanks for your response, but it does not work.
> 

It works if you don't define your fields yourself.

> The table I use has more than five fields. I manually created 
> one field 
> (double clicking the sqlQuery and adding one field).
> When I run the program, I display Query1.FieldCount : 1.
> When I try to display Query1.Fields[1].fieldname ([1], i.e. 
> the second 
> fieldname) I get an "list index out of bounds" error. 
> Displaying Query1.Fields[0].fieldname gives the fieldname of 
> the field I 
> manually created.
> 

If you define one field manually at run-time you have only one field.
Opening the dataset won't add the fields automatically once you defined your
own. I haven't seen this mentioned in fpc/lazarus docs but in Delphi
articles on adding fields at run-time it is stated quite clear: if you want
to add fe. a calculated field at run-time to the existing dataset fkData
fields, you have to define all these fields before adding the new one. If
you have fielddefs for the query you can add the existing fields simply
with:
for i:=0 to MyQuery.FieldDefs.Count-1 do
    Field:=MyQuery.FieldDefs[i].CreateField(MyQuery);
If you don't have fielddefs (0 items) and you don' want to add them in the
designer then just add a 
  SQLQuery1.Active:=true;
  SQLQuery1.Active:=false;
before the above loop to auto fill the fielddefs. For this to work, as for
fields, Fielddefs should be an empty array. As soon on element is in
fielddefs, the auto fill won't work. 

Now, in your previous mail you created the field with

> tmpField:=TStringField.Create(nil);
> tmpField.FieldKind:=fkData;
> tmpField.FieldName:='COUNT';
> MyQuery.Fields.Add(tmpField);
> MyQuery.Open;

This is wrong and fpc 2.7.1 gives even a run-time error saying that dataset
is not set. Replace MyQuery.Fields.Add(tmpField); with
tmpField.Dataset:=MyQuery;. 

Ludo