[英]Filling a TListBox with a column from a database query
I created a table in my database with MYDAC components and added data. 我在数据库中使用MYDAC组件创建了一个表并添加了数据。 How can i extract these values that in colums from this table?
如何从此表中提取这些值?
i tried these but they didn't work; 我尝试了这些,但是它们没有用;
MyQuery1.Close;
MyQuery1.SQL.Text :='SELECT * FROM uyeler ORDER BY site';
Listbox1.Items.Add(MyQuery1.ParamByName('site').AsString);
MyQuery1.Execute;
uyeler = table uyeler =表格
site = colums 站点=列
Editors Note: Based on comments made to accepted answer, this question is asking how to populate a TListBox
with the data returned in a column of a query. 编者注:根据对已接受答案的评论,此问题询问如何用查询列中返回的数据填充
TListBox
。
Your question is a little unclear. 您的问题还不清楚。 You ask how to add column data to a
TListBox
, but your code sample shows something about ParamByName
, which looks like you're trying to assign a ListBox
value to a SQL parameter. 你问如何列数据添加到
TListBox
,但你的代码示例显示了一些关于ParamByName
,它看起来像你想指定一个ListBox
值的SQL参数。
Note : Question clarified based on comment to this reply. 注意 :根据对此回复的评论,问题得到了澄清。 The first code answers the question;
第一个代码回答了这个问题; I'll leave the second as an example for future readers because it's already written.
我将第二个示例留给以后的读者使用,因为它已经写好了。
If you're trying to fill a TListBox
from a database column, you need to run the query, and then loop through the data to add the column data to your TListBox
. 如果尝试从数据库列填充
TListBox
,则需要运行查询,然后遍历数据以将列数据添加到TListBox
。 (You also shouldn't SELECT *
when you're only going to use the site
column; it means extra data is being sent from the database to the application when the data will never be used and will end up being thrown away.) (当您仅要使用
site
列时,也不应SELECT *
;这意味着多余的数据将从数据库发送到应用程序,而这些数据将永远不会被使用并最终被丢弃。)
This should help you get started: 这应该可以帮助您入门:
MyQuery1.Close;
MyQuery1.SQL.Text := 'SELECT site FROM uyeler ORDER BY site';
try
MyQuery1.Open;
ListBox1.Items.Clear;
while not MyQuery1.Eof do
begin
ListBox1.Items.Add(MyQuery1.Fields[0].AsString);
MyQuery1.Next;
end;
finally
MyQuery1.Close;
end;
If you're trying to do the second (populate a parameter with a value from a TListBox
), this should help: 如果您要进行第二次操作(使用
TListBox
的值填充参数),这应该会有所帮助:
// to shorten typing of long lines
var
Site: string;
begin
if ListBox1.ItemIndex <> -1 then
begin
MyQuery1.Close;
MyQuery1.SQL.Clear;
MyQuery1.SQL.Add('SELECT Column1, Column2, site FROM uyeler');
MyQuery1.SQL.Add('WHERE site = :siteval ORDER BY site');
Site := ListBox1.Items[ListBox1.ItemIndex];
MyQuery1.ParamByName('siteval').AsString := Site;
MyQuery1.Open;
try
// Use the database rows here
finally
MyQuery1.Close;
end;
end;
end;
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