index performance tuning in sql server

Permission management is involved in program development. The system uses an integer to record user permissions. The permission level is set: Level1 1 Level2 2 Level3 4 Level4 8 Level5 16 Level6 31 Level7 32 Level8 64 Level9 127 Level10 128 Level11 255 Level12 65535 In the database, if a user A has a permission level of 1, his three

system into multiple nodes, each node's processor can only access its own local resources, is a completely unshared architecture. Data exchange between nodes requires software implementation. Its advantage is that scalability is very good, the disadvantage is that data exchange difficulties with each other, the need to control a lot of software work to achieve communication and task allocation, scheduling, for the general enterprise applications is too complex, inefficient. NUMA (non-uniform

restrictions, then query up, the user will wait longer. Therefore, in this case, we can default to show only the previous 500 records or only the last 30 days of transaction information. In summary, it is a preferred method to increase the performance of the database server on the client side by appropriately adding a query statement that restricts the search scope. Second: Try not to use complex stored

, but the latter is obviously more efficient than the former. Because the latter will not generate a large number of locked table scans or index scans.If you want to check whether a record exists in the table, do not use count (*) as inefficient and waste server resources. It can be replaced by exists. For example: If (select count (*) From table_name where column_name= 'Xxx') Can be written: If exists (select*From table_name where column_na

. Because the latter will not generate a large number of locked table scans or index scans.If you want to check whether a record exists in the table, do not use count (*) as inefficient and waste server resources. It can be replaced by exists. For example:If (select count (*) from table_name where column_name = 'xxx ')Can be written:If exists (select * From table_name where column_name = 'xxx ') You often need to write a t_

When executing SQL queries, the main bottlenecks are: CPU computing speed, large memory cache area When executing SQL queries, the main bottlenecks are: CPU computing speed, large memory cache area 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 i

, which avoids longer locking of the system tables.25. Avoid using cursors as much as possible, because cursors are inefficient and should be considered for overwriting if the cursor is manipulating more than 10,000 rows of data.26. Before using a cursor-based method or temporal table method, you should first look for a set-based solution to solve the problem, and the set-based approach is generally more efficient.27. As with temporary tables, cursors are not unusable. Using Fast_forward cursors

)Untyped XML is not expressed in XML schema. It is saved as a Unicode string in SQL Server. Storage. For their operations, data needs to be converted to the corresponding type. For example (/book/price) [1]> 19.99, Decimal process. A large number of similar comparisons consume a lot of resources, which leads to the importance of type information in XML schema.Type information works in the following aspects

percentage of time that the instruction waits for CPU resources. If more than 25%, indicates CPU tension Select Convert(Numeric (5,4),sum(Signal_wait_time_ms)/sum(Wait_time_ms)) fromsys.dm_os_wait_stats--calculates the percent of ' cxpacket ' for the total wait time --Cxpacket:sql Server is dealing with a very expensive statement, or there is no proper index or filter condition to filter enough records so that the statement will return a large number

; } /// ///User Account/// Public stringUserName {Set;Get; } /// ///User Password/// Public stringPassWord {Set;Get; } /// ///Nickname/// Public stringNickname {Get;Set; } /// ///Encrypted Salt/// Public stringSalt {Set;Get; } /// ///whether to freeze/// Public BOOLIsFrozen {Set;Get; } /// ///Balance/// Public decimalBalance {Set;Get; } /// ///Department/// Public stringDepartme

(T.taskid,'__')= IsNull(N.taskid,'__')Group byT.taskidThe execution plan is as follows: (this looks much simpler than the above, imagine that performance will improve)When the amount of data is large, the performance aspect of using the left join will be greatly improved, note that when on, the null value is converted using IsNull.The two methods can be very different when the data volume

Some common performance problems in SQL Server: 1. When optimizing the query, try to avoid full table scanning. First, consider creating an index on the columns involved in where and order. 2. Try to avoid using left join and null values. Left join consumes more resources than inner join because it contains data that matches null (non-existent) data. Therefore, y

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

server| Problem | performance 1. To optimize the query, you should try to avoid full table scan, first consider the where and the order by the columns involved in the establishment of the index. 2. The null value of the field in the WHERE clause should be avoided as far as possible, or it will cause the engine to discard the use of the index for a full table scan, such as:Select ID from t where num is nullY

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

1. Storage Partition the hard disk into NTFS format. NTFS is faster than FAT32, And you can view the size of your data file. You can use multi-database files for 1 GB or more, in this way, the access load can be distributed to multiple physical hard disks or disk arrays. 2. tempdb Tempdb should also be placed on a separate physical hard disk or disk array. We recommend that you place it on RAID 0 so that it has the highest performance. Do not set the

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

|+---------------------------------+-------+| Log_bin | OFF || Log_bin_basename | || Log_bin_index | || log_bin_trust_function_creators | OFF || log_bin_use_v1_row_events | OFF || Sql_log_bin | On |+---------------------------------+-------+6 rows in Set (0.00 sec)To view the slow query log settings, close by default:Mysql> Show variables like "slow%";+---------------------+-----------------------------+| variable_name | Value |+---------------------+-----------------------------+| Slow_l