with nolock in sql server performance

Label:I used to see my senior developers use with (NOLOCK) when querying in SQL Server and wonder why they use. Now I explored it's and found that it's useful to improve the performance in executing the query . However there is a disadvantage in using it. The disadvantage is, the one of May and not being sure that they

these SQL statements will access, what to do, and then automatically assigns the locks to be used in conjunction with the Set isolation level.Next, let's look at row versioning.2, row version control:Do you want to use it? Small copy:(1), IntroductionRow versioning Isolation is a new isolation framework for SQL Server 20,051. Using row versioning can significant

I used to see my senior developers use with (NOLOCK) when querying in SQL Server and wonder why they use. Now I explored it's and found that it's useful to improve the performance in executing the query . However there is a disadvantage in using it. The disadvantage is, the one of May and not being sure that they was g

Label: I used to see my senior developers use with (NOLOCK) when querying in SQL Server and wonder why they use. Now I explored it's and found that it's useful to improve the performance in executing the query . However there is a disadvantage in using it. The disadvantage is, the one of May and not being sure that the

write cache exists and the algorithm is normal, RAID5 is even better than raid10, although there may not be much difference (here we should assume that there is a certain size of storage, enough write cache, and there is no bottleneck in the CPU for computing and verification ). This is because the raid check is completed in the cache. For example, for RAID 5 of four disks, you can calculate the check in the memory and write three data and one verification at the same time. Raid10 can only wr

addNolockThis approach is not scientific, at least time-consuming. It is not as effective as version control. In addition, unexpected technical problems may exist. You should select the most suitable table to discard the use of the shared lock. Conclusion:NolockAndWith(Nolock: 1: synonym in sql05, only supportedWith(Nolock); 2:With(Nolock. Cross-

About with (nolock) in SQL and withnolock in SQL What does NOLOCK in SQL Server mean? It is generally used in such statements: select * from t with (NOLOCK)

The with (nolock) here refers to the with option in the SQL query, for example: Select * from T1 with (nolock) where a = 'xx' With (nolock) means that no locks are taken into account during query, and dirty reads may be performed. Although dirty reading may occur, it will improve the

SQL Server performance optimization skills, SQL Server Performance Optimization 1. Select the most efficient table name sequence (only valid in the rule-based Optimizer) The SQL

SQL Server address search performance optimization and SQL server performance optimization This is an example of a long time ago. Now, I have no intention of discovering the materials, so I will take it out and try again. 1. Requi

the data is consistent, but nothing is perfect. The cost of the Begin Tran is that all the resources locked by the SQL statements cannot be released until the commit is committed before committing.It can be seen that if the BEGIN TRAN too many SQL statements, the performance of the database is poor. Before this large transaction commits, it is bound to block oth

With the growth of time, the company's database will be more and more, query speed will be more and more slow. Open the database to see hundreds of thousands of of data, the query is inevitable not waste time. To improve SQL query effectiveness, you will generally want to build indexes (index) as the first consideration. In fact, in addition to the establishment of the index, when we are in the SQL command

following is the optimization of the SQL statement in fact, SQL is not complex, but the data of these tables are slightly larger, but also nested inside more complex business logic, history after several rounds of "master" in the index of the whole side of the optimization, can also run normally but over time, the amount of data in the table is getting larger , boiled frog in warm water,

Yesterday's SQL Server query performance optimization-index creation principle (I) mainly introduced the principle. today are some of the main principles and checks the created indexes. Iii. indexing principles In general, building indexes depends on the data usage scenarios. In other words, which SQL statements are co

. Room number andAcquisition Time>='2013-11-6 0:00:00' andAcquisition Time'2013-11-7 0:00:00') Workaround, create a memory table in SQL, first identify the part, and then use the first part of the results to query the final result. It can be checked in seconds. SET STATISTICSIo onDBCCDropcleanbuffers--Turn off cachingDBCCFreeproccache--Turn off cachingSELECTT.* frommeasure_heat TWHERECommunity number=' -' andAcquisition Time=( SELECT min(Acquisit

What exactly does NOLOCK in SQL Server mean?typically used in such statements: SELECT * from T with (NOLOCK)Nolock is a non-locking query that can read data locked by transactions, also known as dirty reads. Description:causes the query for the current session to be blocked

Label:Poptest is the only training institute for developing Test and development engineers in China, aiming at the ability of the trainees to be competent in automated testing, performance testing and testing tools development. In Poptest's LoadRunner training, in order to improve the performance of students experience, add a lot of server optimization knowledge,

When with and as, the expression defines a SQL sentenceCases:WithSonword as(SELECT * FROM person)SELECT * FROM Studentwhere name in (select name from Sonword)EquivalentSELECT * FROM Studentwhere name in (select name from person)With (NOLOCK)Typically used in SELECT statements, data that is locked by a transaction can be readImproves SQL query

Original http://www.cnblogs.com/BoyceYang/archive/2013/06/15/3138142.html Read navigation 1. Overview 2.RulesLogic Database Design 3.EnableDesign with efficient Indexes 4.EnableEfficient Query Design 5.EnableLow performance analysis with technology 6. Summary 1. Overview This is the most effective way to optimize SQL server

SQL Server Performance Tuning methodology and common tools, SQL Server Tuning In earlier articles, we mentioned the DETECT methodology in Performance Tuning. Here we will briefly review the DETECT methodology. Discover the proble