sql server varchar max performance

the same, does not necessarily apply to the current query, the performance problem is generated.Why is the execution plan compiled with a completely inconsistent current, and the cache has not been cleaned up so far? There are two reasons for personal speculation, but it is not entirely certain thatOne is based on the current data distribution (statistical information) obtained by an implementation plan, it may be that the statistics are not accurate

During the work period, the problem of exporting and importing data between databases of different versions is often involved. Simply sort it out and compare the performance. You are welcome to discuss and supplement some methods that are missing. 00. Create a test environment 01. use SQL Server Import and Export Tool 02. Use generate scripts 03. Use BCP

Tags: find combined with server other LTE art definition technology share defaultObjectiveIn this section we continue to talk about index knowledge, before we clustered index, nonclustered index and overlay index, there is also a filter index, through the index filter we can also improve query performance, short content, in-depth understanding.Filter indexes, create nonclustered indexes on query criteria (1

[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

During database design, sometimes attribute record values belonging to the same person are stored in multiple records for the purpose of data standardization, you want to merge multiple attribute data into one row for display. This is a row-to-column conversion. For example, the score table. 1. method 1 (Versions later than SQL2000) -- a total of 1.2 million records SE During database design, sometimes attribute record values belonging to the same person are stored in multiple records for the p

, however, it is very likely that a page stores five data records. Because a column has one or two more bytes, only four data records can be stored. You may think that there is nothing to save one piece of data, but after the data volume is very large, there will be significant performance differences between 4 pieces of data and 5 pieces of data on one page. The reason for storing more data on a page is not to save storage costs, but the hard disk is

occupied storage space. In actual applications, this extreme situation is rare, however, it is very likely that a page stores five data records. Because a column has one or two more bytes, only four data records can be stored. You may think that there is nothing to save one piece of data, but after the data volume is very large, there will be significant performance differences between 4 pieces of data and 5 pieces of data on one page. The reason for

' + CONVERT (VARCHAR (5), @ I )); Insert into tb4040 (c2) VALUES ('test' + CONVERT (VARCHAR (5), @ I )); SET @ I = @ I + 1 END Well, now we can use SSMS to check the space usage of the two tables. If it is SQL2005, you can use the Report provided by SSMS to view the space usage. If it is SQL2008, you can directly view the table space usage on the details page of the object Resource Manager (if you are usin

-side cursorsCompared to server-side cursors, client cursors can reduce server and network overhead and also reduce lockout time.7. Do not ignore the problem of modifying the same record at the same timeSometimes, two users modify the same record at the same time, so that the latter modifies the previous modifier's actions, and some updates are lost. To handle this situation, create a timestamp field, check

Http://www.cnblogs.com/shanyou/archive/2013/02/12/2910232.htmlSQL Server Performance Dashboard reports is a set of Reporting Services reports that are used with reports that are described in SQL Server Management Studio. These reports allow database administrators to quickly determine if bottlenecks exist in their syst

, 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

Label:To test SQL performance:One, by setting statistics to view the system situation when executing SQL. Options: Profile, O, time.SET STATISTICS profile on: Displays the time, in milliseconds, that is required to parse, compile, and execute the query.SET STATISTICS IO on: Reports information about the number of scans per table referenced in the statement, the number of logical reads (pages accessed in the

1. PrefaceFor the optimization of SQL statements or stored procedures, the former mainly use the following statements to determine the specific execution time, but the SQL environment is complex and changeable, the following statement does not accurately determine whether the performance is improved, if you need to know the CPU, IO and other information, there is

During project optimization, I want to analyze SQL server system performance through the database layer. I checked the online code and modified the title and dmvs code, the following code analyzes the SQL statements that are busy after the system runs for a period of time. For reference. Alternative use: When analyzin

At present, I want to analyze the SQL server system performance through the database layer during project optimization.Code, Changed the title and dmvs code. The following code can be used to analyze the SQL statements that are busy in the system after the system runs for a period of time. For reference. Alternative