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允許將明確的值插入資料表的識別欄位中
如果輸入的值大於資料表目前的識別值，SQL Server 會自動利用新插入的值來作為目前的識別值。
Something I stumbled across trying to return a *.csv file to Excel 2000: If the very first text in the file is "ID", Excel will ignore the file extension and attempt to read the file as a SYLK (Symbolic Link) file format.
Just wanted to share this hidden tidbit, in the off-chance that it may save somebody else pain.
-- Rob Storrs, February 15, 2001
指派給：
是否已經核對？否
核對者：
核對日期：2009-09-10 08:17:34
常見問答分類：
| 參考微軟官網，搜尋關鍵字「超大PST和OST檔案的裁工具」 兩工具如下：
根據文件，指出更新程式可避免Outlook允許.pst檔超過2GB的最大容量。
其它官網資訊：
|
|
| Update 同1筆資料列，同1個欄位 | |
| Connection A | Connection B | |
| <1> | Begin Tran | |
| <2> | Select | |
| <3> | | Begin Tran |
| <4> | | Select |
| <5> | | Update (Success) |
| <6> | Update (未執行) | |
| <7> | | Commit Tran |
| <8> | Update (Success) | |
| <9> | Commit Tran | |
| | ※ 在未指定任何參數的情況下，select 並不會造成「鎖定」，而是在update時，才會造成以「資料列鎖定」。 ※ 當先執行update的connection，完成commit 或 rollback的同時，另一connection 的 update才得以繼續執行！ ※ | |
根據「時間管理-給系統管理者 Time Management for System Administrators」這本書所提及的觀念，我於OUTLOOK 2000 中實作了行事曆維護及工作排程。時間是珍貴的東西，對於系統管理者而言尤甚。沒有其他工作會把那麼多領域的事情，一次推給一個人作。使用者經常以他們的請求干擾你，讓你無法完成經理指派給你的長期專案；還有你的電腦就是不聽話，總是在最關鍵的時刻與你耍脾氣。儘管你精通職務上的技術，但是仍然發現必須在晚上和週末加班，只是為了達成一大堆要求。這只會隨著時間，增加自己的壓力。
本書討論的策略，不但幫你解決日常工作，還有能力處理無法避免所產生的突發狀況。作者將自己長期的職業生涯，諸如，支援桌面應用、伺服器管理、以及安全和軟體開發等等，詳實地舉例說明在本書中。這意味著，你將得到有實戰經驗的建言，而非象牙塔般，從未在混沌的網路工作過的陳腔濫調。
在其他技術上，你將學習如何：
- 管理干擾
- 消除時間的浪費
- 保持有效的行事曆
- 將經常發生的事情變成例行公事
- 專注在手邊的工作
- 以客戶預期的事排列優先順序
- 文件化和自動化處理以便快速執行
/*
2009年7月22日下午 12:26:53
使用者: sa
伺服器: 172.17.100.14
資料庫: xxxxdb
應用程式:
*/
'xxxx_tab' 資料表
- 將定義變更儲存至含有大量資料的資料表，可能會需要相當長的時間。儲存變更的期間，將無法存取資料表中的資料。
Cursor Optimization Tips
- Try to avoid using SQL Server cursors, whenever possible.
SQL Server cursors can results in some performance degradation in comparison with select statements. Try to use correlated subquery or derived tables, if you need to perform row-by-row operations.- Do not forget to close SQL Server cursor when its result set is not needed.
To close SQL Server cursor, you can use CLOSE {cursor_name} command. This command releases the cursor result set and frees any cursor locks held on the rows on which the cursor is positioned.- Do not forget to deallocate SQL Server cursor when the data structures comprising the cursor are not needed.
To deallocate SQL Server cursor, you can use DEALLOCATE {cursor_name} command. This command removes a cursor reference and releases the data structures comprising the cursor.- Try to reduce the number of records to process in the cursor.
To reduce the cursor result set, use the WHERE clause in the cursor's select statement. It can increase cursor performance and reduce SQL Server overhead.- Try to reduce the number of columns to process in the cursor.
Include in the cursor's select statement only necessary columns. It will reduce the cursor result set. So, the cursor will use fewer resources. It can increase cursor performance and reduce SQL Server overhead.- Use READ ONLY cursors, whenever possible, instead of updatable cursors.
Because using cursors can reduce concurrency and lead to unnecessary locking, try to use READ ONLY cursors, if you do not need to update cursor result set.- Try avoid using insensitive, static and keyset cursors, whenever possible.
These types of cursor produce the largest amount of overhead on SQL Server, because they cause a temporary table to be created in TEMPDB, which results in some performance degradation.
- Use FAST_FORWARD cursors, whenever possible.
The FAST_FORWARD cursors produce the least amount of overhead on SQL Server, because there are read-only cursors and can only be scrolled from the first to the last row. Use FAST_FORWARD cursor if you do not need to update cursor result set and the FETCH NEXT will be the only used fetch option.- Use FORWARD_ONLY cursors, if you need updatable cursor and the FETCH NEXT will be the only used fetch option.
If you need read-only cursor and the FETCH NEXT will be the only used fetch option, try to use FAST_FORWARD cursor instead of FORWARD_ONLY cursor. By the way, if one of the FAST_FORWARD or FORWARD_ONLY is specified the other cannot be specified.
Difference between Static Cursors and Dynamic Cursors
* A Static Cursor doesn't reflect data changes made to the DB once the ResultSet has been created whereas a Dynamic Cursor reflects the changes as and when they happen.
* A Static Cursor is much more performant than a Dynamic Cursor as it doesn't require further interaction with the DB server.
* A static cursor supports both Relative and Absolute Positioning whereas a Dynamic Cursor supports only Relative Positioning.
* A Static Cursor can be used for Bookmarking purposes as the data returned is static whereas a Dynamic Cursor can't be used for the same.
Static Cursor: A Database Cursor is called a Static Cursor if it captures the snapshot of data only at the time when the ResultSet (or Recordset in case of MS SQL Server) is created with no further DB interaction afterwards. And hence a Static Cursor will be unaware of any data changes made into the database after the ResultSet has been created. A Static Cursor facilitates scrolling through the static ResultSet and it supports both absolute and relative positioning. Reason being, the ResultSet is static and hence the cursor can always be sure of the position of all the records/rows. Relative positioning can be specified in terms of offsets from the current, top or bottom rows.
Dynamic Cursor: A Dynamic Cursor is the one which reflects all the data changes made into the database as and when they happen. This may require continuous re-ordering of data in the ResultSet due to the database changes and hence it's much more expensive than a Static Cursor. The possible re-ordering of records in the ResultSet doesn't allow a Dynamic Cursor to support absolute positioning as it can't be sure of the absolute position of a record/row in the ResultSet. Hence a Dynamic Cursor only supports relative positioning. Furthermore a Dynamic Cursor doesn't support Bookmarks for the obvious reasons.
The article is well worth the read, but here are the main points:
Take a look at the complete article to see Vyas' complete tests to get the entire picture:
[http://vyaskn.tripod.com/differences_between_set_and_select.htm]
select @retid = convert(int,state_class_a) from wid_state_def where wid_state_id = @stateid
if @@ROWCOUNT =0 set @retid = -1 else set @retid = isnull(@retid,0)
CREATE PROCEDURE [dbo].[DatabaseBackup]
@dbname nvarchar(30),
@path varchar(100)
AS
BEGIN
declare @filename nvarchar(60)
declare @weekdayid varchar(1)
declare @db_cnt int
SELECT @weekdayid=DATEPART(weekday, GETDATE())
select @db_cnt=count(*) from master..sysdatabases where name=@dbname
if @db_cnt=0
begin
raiserror(N'資料庫名稱錯誤。', 16, 1)
goto TheEnd
end
if @weekdayid='1'
begin
select @filename=@path+'\'+@dbname+'_Sun.dat'
end
if @weekdayid='2'
begin
select @filename=@path+'\'+@dbname+'_Mon.dat'
end
.
.
.
if @weekdayid='7'
begin
select @filename=@path+'\'+@dbname+'__Sat.dat'
end
BACKUP DATABASE @dbname TO DISK = @filename WITH NOFORMAT, INIT, NAME = @filename, SKIP, NOUNLOAD, STATS = 10
declare @backupSetId as int
select @backupSetId = position from msdb..backupset where database_name=@dbname and backup_set_id=(select max(backup_set_id) from msdb..backupset where database_name=@dbname )
if @backupSetId is null
begin
raiserror(N'確認失敗。找不到資料庫的備份資訊。', 16, 1)
goto TheEnd
end
RESTORE VERIFYONLY FROM DISK = @filename WITH FILE = @backupSetId, NOUNLOAD
TheEnd:
END
Private Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hWnd As Long, ByVal lpOperation As String, ByVal lpFile As String, ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long
Private Sub LblLink_Click()
ShellExecute hWnd, "open", "http://bbs-mychat.com/index.php", vbNullString, vbNullString, conSwNormal
End Sub
Private Sub LblLink_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
LblLink.FontBold = True
LblLink.FontUnderline = True
LblLink.ForeColor = vbBlue
Me.MousePointer = 99
End Sub
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
LblLink.FontBold = False
LblLink.FontUnderline = False
LblLink.ForeColor = vbBlack
Me.MousePointer = 0
End Sub
