---- Set a non-primary key to clustered index [Step 4] to: http://king123654789.iteye.com/blog/1169191
1. View All indexes. Clustered indexes are created on the primary key by default.Sp_helpindex person
2. -- delete the primary key constraint and remove the index constraint on the primary key queried in [1], for example, PK _ person _ 117F9D94. Remove the primary key constraint from the primary key field
, how can we tell which tables need to be indexed and which are not?Typically, SQL Server executes a query script with an existing index, and if no index is found, it is automatically generated and stored in the DMV (dynamic management view). This information is purged whenever the
SELECT TOP 1000O.name as table name, I.name as index name, i.index_id as index ID, dm_ius.user_seeks as Search times, Dm_ius.user_scans as Scan count, dm_ius.user_lookups as lookup times, dm_ius.user_updates as update number, p.tablerows as table row count, ' DROP INDEX ' + QUOTENAME (i.name)+ ' on ' + QUOTENAME (s.name) + '. ' + QUOTENAME (object_name (Dm_ius. o
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
Label:Objective About SQL Server Tuning series is a huge content system, not a word two words can be analyzed clearly, this article first in the SQL tuning in the most commonly used query plan to parse, to do a good job of the basic grasp, tamping basic skills! Then we talk
Tags: ATI latest sel Opening technical file reference tis onlineNow has been doing the project, the amount of data is relatively small, at the beginning of the time did not feel, because it is just beginning, the amount of data is very small, in the process of the use of speed is very fast, but with the constant growth of data volume, found that the program is more and more slow, even the problem of timeouts, so to the program Early project is relatively tight, not for the Big Data volume busine
Tags: style blog http io ar color using SP on This experience uses the SQL database migration Wizard (SQLAZUREMW) to migrate SQL Server 2008 databases to Azure SQL database. Of course, SQLAZUREMV can also migrate SQL
clustered index, nonclustered index, nonclustered unique indexWe all know that establishing an appropriate index can improve query speed and optimize queries. First, whether a clustered or nonclustered index is a B-tree structure .
The
clustered index matches th
can avoid Key lookup is perfect, let's revise non-clustered index to include it in the index with the Include keyword His fields are:[SQL]
DROP INDEX idx_non_clust_salesorddetaildemo_modifieddate on salesorddetaildemo
GO
CREATE nonclustered INDEX idx_non_clust_sale
Label:clustered index, nonclustered index, nonclustered unique index We all know that establishing an appropriate index can improve query speed and optimize queries. First, whether a clustered or nonclustered index is a B-tree structure .
The
clustered
is much higher than that of the composite Index query efficiency, while in 11.2.0.3 version Verify that the ad hoc query efficiency of the common composite index is more efficient than the efficiency of the bitmap index) Create TableT (name_id, gender not NULL, location not NULL, Age_range not NULL, data) as Selectrownum, Decode ( Floor(Dbms_random.value (0,2))
query logical reads 20 times, pre-read 2 times, no physical read ..., and the table with the clustered index logic read 23 times, read 22 times! There are also statistical inaccuracies that result in physical reads 1 times! .... So it's a lot better than a stack table scan.Of course, in order to further analysis, in fact, the reason for the difference is simple: The table with the clustered index because o
, with a logical IO of 23 times, and read-ahead soared to 22 times.In comparison:The same query statement, the heap table query logical reads 20 times, pre-read 2 times, no physical read ..., and the table with the clustered index logic read 23 times, read 22 times! There are also statistical inaccuracies that result in physical reads 1 times! .... So it's a lot better than a stack table scan.Of course, in order to further analysis, in fact, the reaso
any questions, you can leave a message or private messages, and look forward to an in-depth study of your child's shoes with SQL Server. Learn together and progress together.At the end of the article gives the previous several connections, the following content basically covers our daily write query operation decomposition, it seems necessary to sort out a directory ....
in-depth study of your child's shoes with SQL Server. Learn together and progress together.At the end of the article gives the previous several connections, the following content basically covers our daily write query operation decomposition, it seems necessary to sort out a directory ....SQL Server
SQL Server Tuning Series Article summary: This is a series of articles on SQL Server tuning, which basically covers the decomposition of the query operations we write in the day and the tuning
Tags: Traverse employee acquisition leads to centralized filter structure SRC spanThis article is "Stairway Series:Part of the ladder for SQL Server indexingIndexes are the basis of database design and tell developers to use the database with regard to the designer's intentions. Unfortunately, when performance problems arise, indexes are often added as an afterthought. The end here is a simple series of art
the importance of statistical information is self-evident. Interested children's shoes can be noticed in advance.The content of SQL Server performance tuning involves a wide range of topics, followed by an analysis in the following article.If you have any questions, you can leave a message or private messages, and look forward to an in-depth study of your child'
in the data, you cannot create a unique index, a unique constraint, or a PRIMARY key constraint.
A unique nonclustered index can include a non-key column that contains sex.
a unique index relies on a unique constraint, and deleting a unique index must remove a unique constraint. In addition ,
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