其实这个东西挺烦的，不小心点错了会开好多窗口，所以我决定把他隐藏了，要隐藏他就必须要用 Firefox 的 userChrome.css 文件了。
开 始 -> 运行 -> 输入 %AppData%\Mozilla\Firefox\Profiles，然后进入里面类似 xxxxxxx.default 的目录，再进入 chrome 目录，把文件 userChrome-example.css 改名为 userChrome.css。
然后修改 userChrome.css 文件，增加下面的 CSS 语句：
menupopup[placespopup="true"] > menuseparator:nth-last-child(-n+2),
menupopup[placespopup="true"] > menuseparator:nth-last-child(-n+2) + menuitem
{
display: none !important;
}
private bool CheckCardNumber(string number)
{
int[] iW = new int[] { 7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2, 1 };
int iSum = 0;
for (int i = 0; i < 17; i++)
{
int iVal = 0;
int.TryParse(number[i].ToString(), out iVal);
iSum += iVal * iW[i];
}
int iCheck = iSum % 11;
string check = string.Empty;
switch (iCheck)
{
case 0: check = "1"; break;
case 1: check = "0"; break;
case 2: check = "x"; break;
case 3: check = "9"; break;
case 4: check = "8"; break;
case 5: check = "7"; break;
case 6: check = "6"; break;
case 7: check = "5"; break;
case 8: check = "4"; break;
case 9: check = "3"; break;
case 10: check = "2"; break;
}
string valid = number[17].ToString().ToLower();
return valid == check;
}
最常用的 T-SQL 语句：
DELETE FROM [dbo].[myTable] WHERE 主键 NOT IN
(SELECT MAX(主键) From [dbo].[myTable] GROUP BY 列1, 列2, 列3)
SQL Server 2005 及以上版本，用 CTE：
WITH tmpOrderdTable
AS
(
SELECT
GroupID = ROW_NUMBER() OVER (PARTITION BY 列1, 列2, 列3 ORDER BY 主键)
FROM
[dbo].[myTable]
)
DELETE FROM tmpOrderdTable WHERE GroupID > 1
为了提高效率可以先开启单人存取模式，删除完再恢复多人存取模式：
# 开启单人存取模式
USE [master]
ALTER DATABASE [myDB] SET SINGLE_USER WITH ROLLBACK IMMEDIATE
# 开启多人存取模式
USE [master]
ALTER DATABASE [myDB] SET MULTI_USER WITH ROLLBACK IMMEDIATE
比如有文章表 Article(Id,Category,InsertDate)
现在要用SQL找出每种类型中时间最新的前N个数据组成的集合
SELECT A1.*
FROM Article AS A1
INNER JOIN (SELECT A.Category,A.InsertDate
FROM Article AS A
LEFT JOIN Article AS B
ON A.Category = B.Category
AND A.InsertDate <= B.InsertDate
GROUP BY A.Category,A.InsertDate
HAVING COUNT(B.InsertDate) <= @N
) AS B1
ON A1.Category = B1.Category
AND A1.InsertDate = B1.InsertDate
ORDER BY A1.Category,A1.InsertDate DESC
@N 就是要取多少条
ALTER FUNCTION [dbo].[UF_SpliteIntToTable]
(
@String VARCHAR(8000)
)
RETURNS @Table TABLE (Id INT)
AS
BEGIN
DECLARE @SpliteChar AS CHAR(1) = ',';
WITH TempTable AS
(
SELECT CAST(SUBSTRING(@String,1,CHARINDEX(@SpliteChar,@String,1) - 1) AS INT) AS item,
SUBSTRING(@String,CHARINDEX(@SpliteChar,@String,1) + 1, LEN(@String)) + @SpliteChar AS list
UNION ALL
SELECT CAST(SUBSTRING(list,1,CHARINDEX(@SpliteChar,list,1) - 1) AS INT) AS item,
SUBSTRING(list,CHARINDEX(@SpliteChar,list,1) + 1, LEN(list)) AS list
FROM TempTable
WHERE LEN(TempTable.list) > 0
)
INSERT INTO @Table SELECT item FROM TempTable WHERE item > 0
RETURN
END