I've got a SQL Server table with about 50,000 rows in it.我有一个SQL Server表,其中包含大约50,000行。I want to select about 5,000 of those rows at random.我想随机选择大约5,000行。I've thought of a complicated way, creating a temp table with a "random number" column, copying my ...
SELECTtop1[ActivityID] ,[CardNo] ,[Password] ,[State] ,[CreateTime] ,NEWID()asRandom FROM[TGBus_Card].[dbo].[Ka_Card]WhereActivityID=501AndState=0OrderByRandom Select[语句执行花费时间(毫秒)]=Datediff(ms,@d,Getdate()) 确实有所提高!!但太不明显了。。。 还有没有更好的办法?! 于是我又...
ALTER PROCEDURE [dbo].[usp_RandomNumber] ( @Len INT = 1, --随机数位数 @Rows INT = 1 --随机笔数 ) AS BEGIN DECLARE @T AS TABLE([Random Number] VARCHAR(MAX)) DECLARE @L INT = 1, @R INT = 1 WHILE @R <= @Rows BEGIN DECLARE @RN varchar(MAX) = '' WHILE @L <= @Len -...
(@namenvarchar(100) )returnsnvarchar(50)asbeginreturn'value';endgoselectdbo.performance_tuning_randomString('dada');--declare and set valuegodeclare@valuenvarchar(max)=N'dada';set@value=N'super';--select @value = count(*) from @table;print@value;go--if else, begin end 不一定需要godeclar...
Declare @d DatetimeSet @d=getdate()SELECT top 1[ActivityID],[CardNo],[Password],[State],[CreateTime],NEWID() as RandomFROM [TGBus_Card].[dbo].[Ka_Card] WhereActivityID=501AndState=0Order By RandomSelect [语句执行花费时间(毫秒)]=Datediff(ms,@d,Getdate()) ...
select data_1.tid1,data_1.id from row_num as row_num inner join data_1 as data_1 on data_1.tid1 = row_num.tid2 最后轮到 POSTGRESQL , 但是这样做性能在大数据量上是一个问题。 select d.* from (select floor(random() * (max(id) - min(id))) as id from test_d) as ma ...
先从概念说起,我们看下SQL SERVER是如何启动Statistics这个特性的。如果没有启动我们就要手工启动: select name,is_auto_create_stats_incremental_on,is_auto_update_stats_on,is_auto_update_stats_async_on ,is_auto_create_stats_on from sys.databases ...
This trace flag isn't required starting with SQL Server 2016 (13.x), as minimal logging is turned on by default for indexed tables. In SQL Server 2016 (13.x), when the bulk load operation causes a new page to be allocated, all of the rows sequentially filling that new page are ...
The following example updates the VacationHours column by 25 percent for 10 random rows in the Employee table. SQL Copy USE AdventureWorks2022; GO UPDATE TOP (10) HumanResources.Employee SET VacationHours = VacationHours * 1.25 ; GO If you must use TOP to apply updates in a meaningful ...
Random r =newRandom(0);stringinitialDataFile =".. \\.. \\UserIDLatLon.txt"; FileStream ofs =newFileStream(initialDataFile, FileMode.Create); StreamWriter sw =newStreamWriter(ofs);for(inti =0; i <1000000; ++i) {doublelat = (90.0- (-90.0)) * r.NextDouble() + (-90.0);doub...