sql server sparse columns performance

as pointers to create associations in records on different pages. This behavior takes a name in the SQL Server database called a row overflow.　　Third, the negative impact of row overflow on database performance.Having mastered the basic workings of the data page above, the database administrator needs to focus on understanding the adverse impact of row overflow on database

Label:It is understood that the vast majority of developers understand the index is smattering, limited to the majority of daily work without opportunities, and what is not necessary to care about the index, it is a query is too slow to find the query criteria to build an index OK, which day and a query slow, and then build an index is, Or simply the entire query SQL directly to the DBA, so that the DBA directly help to optimize, so the situation is t

Performance Comparison Between ISNULL and COALESCE in the paging mode of SQL Server, isnullcoalesce Preface In the previous section, we explained the data type and several notes in the string. In this section, we will continue to talk about the number of string lines, other content and interspersed content, short content, and in-depth explanation. (For details, s

[sal]>25000/12; 10, different types of index performance is not the same, should be used as far as possible first high-performance The index lookup efficiency of a numeric type is higher than the string type, and the index of fixed-length string char, nchar is higher than the variable-length string varchar, nvarchar. (inefficient) Select ... from tableName where Username= ' Zhang San ' and age>=21 (efficie

Long time no article, before the system officially launched, the DBA will generally test the performance of the serverFor example you have a lot of servers, some do Web server, some do cache server, some do file server, some do database serverThe server to do the database

not fully covered, at least to explain a part. Above we get the results to view the execution time, now let's look at both the query execution plan. Select COALESCE (select MAX (index_id) from sys.indexes WHERE [object_id] = t.[object_id]), 0) from sys.tables as T; select ISNULL (SELECT MAX (index_id) from sys.indexes WHERE [object_id] = t.[object_id]), 0) from sys.tables as T; The above may not be accurate, but also related to hardware configuration, it is possible to coale

not necessarily the true inner join:SELECT A.* FROM A INNER JOIN B ON A.KEY=B.KEYMay or may not require party B to be in the execution plan based on what constraints exists. If A.key is an empty foreign key reference B.key, then the optimizer cannot from it must confirm that a B row exists, and each row is scheduled to fall B. If A.key is a mandatory foreign key reference B.key, then the optimizer is free to guarantee the existence of the line from the constraints of the plan to reduce B. Howev

not regular, it is time-consuming to index the above, so the efficiency is lower than using the self-increment field.3, CombGiven the pros and cons of the two primary key types above, the comb type can be used to find a balance for both. Its design idea is this: since the GUID type has no regularity can be made index inefficient, affecting the performance of the system, then can not be combined to preserve the GUID of the first 10 bytes, with the lat

Label:Original: SQL Server database Performance tuning tipsThe reasons for the slow query are many, and the following are common: 1. No index or index is not used; 2, I/O throughput is small, forming a bottleneck effect; 3, insufficient memory; 4, the network speed is slow; 5, the amount of data queried is too large; 6, lock or deadlock; 7, the return of unnecess

Original: Set STATISTICS io and set STATISTICS time in SQL Server query performance optimizationIn recent times, has been exploring the SQL Server query performance issues, of course, also aimless search for a lot of information,

Label:Reprint Link: http://www.cnblogs.com/knowledgesea/p/3683505.htmlOverview of ToolsIf you have a database application system, there are a large number of tables, views, indexes, triggers, functions, stored procedures, SQL statements, and so on, and the performance of the poor, and the bitter you have to optimize it, then what should you do? Brother teaches you, first you need to know where the problem i

, and the virtual memory counters are two main: Paging file:% usage to monitor the usage ratio of Paging File instances Process:paging File Bytes to monitor the size of virtual memory The more data stored in virtual memory, the greater the gap between the amount of physical memory and the actual demand, the ratio% Usage is only as a reference value, and if the long time is close to 100%, then the system is likely to be abnormal. Second, monitor

that go through it so that there's no point in having to perform performance tuning later on. Well, back to the topic, let's look at stream Aggregate.Stream AggregateThe concepts on MSDN are as follows: the Stream aggregate operator groups rows by one or more columns, and then computes one or more aggregate expressions returned by the query. The output of this operator can be referenced by subsequent opera

Foreword: This article is to blog http://www.dbnewsfeed.com/2012/09/08/5-performance-killers-when-working-with-linked-servers/ Translation, if the translation is not good or bad place, please point out, we study progress together. Respect the original and translated labor results, please indicate the source when reproduced. Thank you!When using a linked server (Linked Servers), the most expensive cost is th

will query through the indexed range query LODGING_PKBecause the index range query will return a set of values, its efficiency will be the peso cited as the only scan lowerExample 2SELECTfromUserWHERE='mrzhang ';This SQL is executed in two steps, Lodging$manager the index range query (get all rowid that match the condition record), and get the value of the lodging column through the ROWID Access table.Because Lodging$manager is a non-unique index, th

a clustered index on the view to make it an INDEX view create unique clustered index IndexPOView ON POView (PurchaseOrderID) GO You can compare the query statement with the execution plan of the query index view. The index view provides better query performance: The SQL Server Query Optimizer always tries to find the best execution plan. Sometimes, although yo

, without being hindered by interaction. Like what: Use a specific report server as a front-end server to process all report creation requests, so that other servers are free to process interactive reports. Use one or more report servers to handle the production of ordered subscriptions or event-driven reports. General performance

Label:Currently in a project optimization, want to analyze SQL Server system performance through the database layer, check the online code, modify the title and DMVs code, the following code can be used to analyze the system after a period of time, those statements are system busy SQL statement. As a reference. Alterna

Orders table. Here, by the way. If you introduce a static variable, SQL Server automatically parameterize the value to reduce the number of compilations and reuse the execution plan. Because lookups only search for those pages that meet the criteria, the lookup efficiency is only proportional to the number of rows and pages that match the criteria, and does not relate to total rows in the entire table. C,