问题
I want to fill my combobox with data from a SQL database but it doesn't work. My query has a connection to the database, query SQL property field is select * from provider_table
Query1.SQL.Clear;
Query1.SQL.Add('select name from provider_table where region_code = '+quotedstr('eng')');
Query1.Open;
while NOT Query1.Eof do begin
ComboBox1.Items.Add(Query1['name']);
Query1.Next;
end;
Does anyone have an idea? Thanks for the answers!
回答1:
Is this what you are looking for?
procedure SelCombo(sql:ansiString;Q:TSQLQuery; var Combo:TComboBox);
var i: integer;
begin
Q.Close;
Q.SQL.Text:='';
Q.Open(sql);
Combo.Text:='';
while not Q.Eof do begin
Combo.Items.Add(Q.Fields.Fields[0].AsString);
Q.Next;
end;
Q.Close;
end;
回答2:
This isn't so much about the combo-box as whether you're getting anything returned from your query. The first thing to do is ensure that the query is working. I'd first put a TMemo or TList on the form and mess with the query until it's returning the data you're expecting.
Alternatively, drop a DB-aware component on the form and hook it to the TSqlQuery component to verify you're getting a non-empty result set.
"Select * from provider_table" may well be returning items, but the query in the example is far more specific and it may not be returning anything.
Once you've verified you're getting a non-empty result set, THEN fill up the combo-box.
Ensure that its style property is set to "Dropdown List" so the user can only select from the returned items.
Also, FWIW, lists of items placed into combo-boxes like this from database queries are, more often than not, lists of foreign keys from another table than what you're dealing with. So a DB-combobox that allows foreign-key selection to fill it up is a much better way to go than the approach you're using. You set a couple of properties in the Object Inspector and it fills itself when the form loads.
It's also common in such situations that the string displayed in the combo-box is also NOT the value used as the key in the table or as the foreign-key value. Instead, an index (number) might be used. This requires a lookup property where the selected item is mapped to another value that the database tables use. (Not all combo-boxes are the same when it comes to DB uses!)
来源：https://stackoverflow.com/questions/24597682/delphi-filling-combobox-items-from-sql-database