Following is the code snippet which will show you how to use ADOQuery in Delphi XE2?
function TClass1.UseADOQuery : integer;
begin
try
with qryADOQuery do
begin
Connection := ADOConnection; //Connection name
Close;
SQL.Clear;
SQL.Text :=
'SELECT ColumnX FROM TableA WHERE ' +
'ColumnA = :ParameterA AND ' +
'ColumnB = :ParameterB AND ' +
'ColumnC = :ParameterC';
Parameters.ParamByName('ColumnA').Value := ParameterA;
Parameters.ParamByName('ColumnB').Value := ParameterB;
Parameters.ParamByName('ColumnC').Value := ParameterC;
Open;
if (Recordcount = 0) then
result := 0
else
result := Fields.FieldByName('ColumnX').Value; //Assume ColumnX value is an integer
Close;
end;
except
on E : Exception do
begin
result := 0;
ShowMessage('Error occured in function UseADOQuery: ' + E.Message);
exit;
end;
end;
end;
Explanation:First of all query has be be initialized with connection name. Now close it if already opened. For being on safer side, we should close it first before using it. Clear the SQL statement if any then write new SQL statement. Parameters to the query are passed by using colon (:) keyword. Recordcount keyword returns the number of rows affected.
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