如果是其他数据库一般也不缩小，为了性能，它的空间还留着,再写入的时候用这些空间。
如果是Paradox or dBASE使用是物理删除。
//Delphi中的BDE的帮助中的示例
procedure PackTable(Table: TTable);
var
Props: CURProps;
hDb: hDBIDb;
TableDesc: CRTblDesc;
begin
// Make sure the table is open exclusively so we can get the db handle...
if not Table.Active then
raise EDatabaseError.Create('Table must be opened to pack');
if not Table.Exclusive then
raise EDatabaseError.Create('Table must be opened exclusively to pack');
// Get the table properties to determine table type...
Check(DbiGetCursorProps(Table.Handle, Props));
// If the table is a Paradox table, you must call DbiDoRestructure...
if Props.szTableType = szPARADOX then begin
// Blank out the structure...
FillChar(TableDesc, sizeof(TableDesc), 0);
// Get the database handle from the table's cursor handle...
Check(DbiGetObjFromObj(hDBIObj(Table.Handle), objDATABASE, hDBIObj(hDb)));
// Put the table name in the table descriptor...
StrPCopy(TableDesc.szTblName, Table.TableName);
// Put the table type in the table descriptor...
StrPCopy(TableDesc.szTblType, Props.szTableType);
// Set the Pack option in the table descriptor to TRUE...
TableDesc.bPack := True;
// Close the table so the restructure can complete...
Table.Close;
// Call DbiDoRestructure...
Check(DbiDoRestructure(hDb, 1, @TableDesc,
nil, nil, nil, False));
end
else
// If the table is a dBASE table, simply call DbiPackTable...
if (Props.szTableType = szDBASE) then
Check(DbiPackTable(Table.DBHandle, Table.Handle, nil, szDBASE, True))
else
// Pack only works on PAradox or dBASE; nothing else...
raise EDatabaseError.Create('Table must be either of Paradox or dBASE ' +
'type to pack');
Table.Open;
end;
