1.C#.NET 字符串转数组，数组转字符串

             string str = "1,2,3,4,5,6,7";

            string[] strArray = str.Split(','); //字符串转数组

            str = string.Empty;

            str = string.Join(",", strArray);//数组转成字符串

2.c# 三种取整方法 向上取整 向下取整 四舍五入

            Math.Round：四舍六入五取整

            Math.Ceiling：向上取整，只要有小数都加1

           Math.Floor：向下取整，总是舍去小数

3.SqlServer 查询死锁，杀死死锁进程

       

-- 查询死锁select        request_session_id spid,       OBJECT_NAME(resource_associated_entity_id) tableName    from        sys.dm_tran_locks   where        resource_type='OBJECT'

 

--杀死死锁进程kill 354

 

4、查询在一个个表中有另一个表中没有的数据

select   UserId,UserName   from   Users where UserId NOT in(select UserId from  PxbUser  where Users.UserId=PxbUser.UserId and PxbId=1)select   UserId,UserName   from   Users  where (select count(1) as num from PxbUser where PxbUser.UserId = Users.UserId and PxbUser.PxbId=1) = 0   --效率更高