identify poor performance in sql server

Http://blog.csdn.net/tuoxie5431/archive/2010/01/19/5214010.aspx When executing SQL queries, the main bottlenecks are: CPU computing speed, memory cache size, and disk Io speed. For queries of large data volumes, the bottleneck is generally concentrated on disk Io and memory cache. In order to improve the efficiency of SQL queries, we need to minimize the number of data entries designed for queries-create a

) include (Gender,createtime) You can see that we have modified the index after using include Gender,createtime, the index Ix_username has reached the full coverage of all the columns of the datasheet users, at which point there is no doubt that Query 2, query 3 does not appear bookmark lookup, The bookmark lookup for query 4 also disappears. At this point the index ix_username structure is as follows Index Ix_username has reached the full coverage of the users table, for our qu

;, ②. Multiple columns are frequently accessed at the same time, and each column contains duplicate values. You can consider creating a composite index; ③ Composite indexes should try to overwrite key queries, and the leading column must be the most frequently used column. 2. is null and IS NOT NULL Null cannot be used as an index. Any column containing null values will not be included in the index. Even if there are multiple columns in the index, as long as one of these columns contains null, t

SQL Server Performance Optimization (1) Database Design Can you refer to the recent forum on the emergence of an excellent post http://topic.csdn.net/u/20100415/10/a377d835-acbd-4815-8bcb-b367f88ac8b5.html? 92227Database design includes physical design and logical design:Physical DesignYou can use the raid hardware architecture.To put it simply, the usage policy

Label:Source: When SQL Server creates a composite index, the composite index column order affects the performance of the query Talk about composite indexes Write index blog Too much, has not wanted to write, there are two reasons:One is the suspicion that there are fried leftovers, brothers have said: Index, as long as the query criteria to build the index on the

Label:In the initial SQL Server performance issue (2/4), we discussed the list of waiting resources or running session scripts. In this article we will look at how to list blocked sessions with specific information. 1 /******************************************************************************************/ 2 CREATE FUNCTION [Dbo].dba_getstatementforspid3 ( 4

frequently (by the way, it becomes a clustered index), and can better meet most of our needs. The auto-increment ID column is omnipotent. The Int type only occupies 4 bytes to fully meet the requirements of narrow indexes. The absolute sequential storage can effectively reduce index fragmentation, which fully conforms to our table habits, it is always correct to use an auto-increment ID column as the primary key. Here, the key columns of clustered indexes are mainly for query consideration. S

First, Introduction Recently, a customer has noticed a high counter (forwarded records/sec), with intermittent disk wait queue fluctuations. This article shares what is the forwarded record and discusses in principle why the forwarded record creates additional IO. Second, the principle of storage In SQL Server, when data is stored as a heap, the data is unordered, and pointers to all nonclustered indexes

, and query 4, the query can only be completed by indexing IX_UserName, without the need to perform a bookmarked search. Now let's take a look at the overhead and query plan of these two queries. We can see that we do not need to prompt the index. The query optimizer has automatically selected our index, logical reads also dropped to 2 times Users UserName Users ((IX_UserName)) UserName For more information about Include, see the include charm in

(IX_UserName)) where UserName like 'ja%' For more information about Include, see the include charm in SQL Server indexes (indexes with contained columns) It is explained that the bookmarked search has a great impact on the query performance and is basically inevitable. This does not mean that the bookmarked search is a great beast. We didn't know what a bookmar

dropped to 2 times Select * FromUsersWhereUsernameLike 'Ja %'Select * FromUsersWith(Index(Ix_username ))WhereUsernameLike 'Ja %' For more information about include, see the include charm in SQL Server indexes (indexes with contained columns) It is explained that the bookmarked search has a great impact on the query performance and is basically inevitab

Users with(index(IX_UserName)) where UserName like 'ja%' For more information about Include, see the include charm in SQL Server indexes (indexes with contained columns) It is explained that the bookmarked search has a great impact on the query performance and is basically inevitable. This does not mean that the bookmarked search is a great beast. We didn't kn

I/O performance diagnostics SQL Server performance is very dependent on the I/O subsystem. Unless your database is fit for physical memory, SQL Server often has database pages in and out of the cache pool. In this way, the actual

executes. Examples are as follows: SET STATISTICS profile on SET STATISTICS IO on SET STATISTICS time on GO – Your SQL script starts SELECT [TestCase] from [Testcaseselect] – Your SQL script is over GO SET STATISTICS Profile OFF SET STATISTICS IO OFF SET STATISTICS Time OFF Alternatively, you can determine how efficient the SQL statement is by adding statements

index controls the order of data rows based on key-value fields. Because SQL SERVER sorts data rows by the key-value fields of clustered indexes, when you need to sort certain fields, use these fields as the key-value of clustered indexes, creating a clustered index will greatly improve the query performance. Because the data has been sorted in the order of the