خواندن تمام رکوردهای یک جدول در TstringGrid
Loading millions of records into a stringlist can be very slow /}
procedure TForm1.SlowLoadingIntoStringList(StringList: TStringList);
begin
StringList.Clear;
with SourceTable do
begin
Open;
DisableControls;
try
while not EOF do
begin
StringList.Add(FieldByName('OriginalData').AsStrin g);
Next;
end;
finally
EnableControls;
Close;
end;
end;
end;
{/ This is much, much faster /}
procedure TForm1.QuickLoadingIntoStringList(StringList: TStringList);
begin
with CacheTable do
begin
Open;
try
StringList.Text := FieldByName('Data').AsString;
finally
Close;
end;
end;
end;
{/ How can this be done?
In Microsoft SQL Server 7, you can write a stored procedure that updates every night
a cache table that holds all the data you want in a single column and row.
In this example, you get the data from a SourceTable and put it all in a Cachetable.
The CacheTable has one blob column and must have only one row.
Here it is the SQL code: /}
Create Table CacheTable
(Data Text NULL)
GO
Create
procedure PopulateCacheTable as
begin
set NOCOUNT on
DECLARE @ptrval binary(16), @Value varchar(600) -
- a good Value for the expected maximum Length
- - You must set 'select into/bulkcopy' option to True in order to run this sp
DECLARE @dbname nvarchar(128)
set @dbname = db_name()
EXEC sp_dboption @dbname, 'select into/bulkcopy', 'true'
- - Declare a cursor
DECLARE scr CURSOR for
SELECT OriginalData + char(13) + char(10) - - each line in a TStringList is
separated by a #13#10
FROM SourceTable
- - The CacheTable Table must have only one record
if EXISTS (SELECT * FROM CacheTable)
Update CacheTable set Data = ''
else
Insert CacheTable VALUES('')
- - Get a Pointer to the field we want to Update
SELECT @ptrval = TEXTPTR(Data) FROM CacheTable
Open scr
FETCH Next FROM scr INTO @Value
while @ @FETCH_STATUS = 0
begin - - This UPDATETEXT appends each Value to the
end
of the blob field
UPDATETEXT CacheTable.Data @ptrval NULL 0 @Value
FETCH Next FROM scr INTO @Value
end
Close scr
DEALLOCATE scr
- - Reset this option to False
EXEC sp_dboption @dbname, 'select into/bulkcopy', 'false'
end
GO
{/ You may need to increase the BLOB SIZE parameter if you use BDE /}
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