sql query performance tuning tips

SQL Server query performance optimization and analysis of transactions and locks (1) Step 2: analyze the locking status using SQL statements. sys. in the sysprocesses view, find out the source of waiting for the initial lock of resources and the subsequent processes to be forced to stop. The following code is applicabl

The SQL Server compact product group published a blog article about how to improve the query performance of the SQL Server compact database. It is comprehensive and authoritative. We suggest you take a look. In fact, the SQL Server compact online series has provided a detail

Tags: analyze one moni min sim data soft databases ImpConnection poolhttps://www.mssqltips.com/sqlservertip/5630/understanding-sql-server-connection-pooling-in-adonet/Open Activity Monitorhttps://docs.microsoft.com/en-us/sql/relational-databases/performance-monitor/ open-activity-monitor-sql-server-management-studio?vi

This article describes how to optimize the data that will affect the query performance when performing SQL queries. For more information, see explain. This article describes how to optimize the data that will affect the query performance when performing

Recently, in the tuning of a customer to find a very interesting phenomenon, for a complex query (involving 12 tables) to establish the necessary index, the statement used by the IO dropped sharply, but the execution time does not fall, from the original 8 seconds to 20 seconds. By observing the execution plan, we found that the previous execution plan used a hash join for many of the large table connectio

Recently in the tuning of a customer to find a very interesting phenomenon, for a complex query (involving 12 tables) to establish the necessary indexes, the statement used by the IO dropped sharply, but the execution time does not drop the reverse rise, from the original 8 seconds to 20 seconds. By observing the execution plan, it was found that the previous execution plan used a hash join in many large ta

overlay index becomes very wide, then you can consider an index connection.For this sentence SQL (select Username,gender from dbo. UserInfo where username= ' userN600 ' and gender=1 ' can build a nonclustered index on the Gender.For this example, it is possible that the SQL optimizer does not use both the nonclustered index ix_username and our newly established index on gender, so we can tell the

V_cust_rcvlbesWHERE postcode> "98000"The number of rows in the view is less than the rows in the primary table, and the physical order is the required order, reducing disk I/O, so the query effort can be significantly reduced. 23, you can use distinct without GROUP bySELECT OrderID from Details WHERE UnitPrice > Ten GROUP by OrderIDCan be changed to:SELECT DISTINCT OrderID from Details WHERE UnitPrice > 10 24. Use UNION ALL to not use UnionUNION all

Common performance query SQL statements -- View table locksSelect * From SYS. V _ $ sqlarea where disk_reads> 100 -- Waiting for monitoring casesSelect event,Sum (decode (wait_time, 0, 0, 1) "Prev ",Sum (decode (wait_time, 0, 1, 0) "curr ",Count (*) "tot"From v $ session_waitGroup by eventOrder by 4 -- Rollback segment contentionSelect name, waits, gets, Waits/ge

The person who writes the program often needs to analyze whether the SQL statement that has been written has been optimized, and how fast the server responds, this time it needs to use the statistics state value of SQL to view it. by setting statistics we can view the system situation when executing SQL. The options are Profile,io, time. Introduced as follows:SET

SQL statement Stored Procedure query performance test comparison code. SQL statement Stored Procedure query performance test comparison code. 1. Create Database Liezui_Test ID int primary key auto-Increment Title varchar (100)

Tags: style blog http using strong data SP on C 1. Table Definition(1) If the string field is often needed, can be redundant, otherwise do not redundant(2) A field that is often required as a where query condition can be indexed, but too many indexes affect the performance at write time(3) Reasonably define the data type of the field(4) Separate tables for storing attachments or large (super) text(5) The f

BuniessDateTime1 between ' 2016-6-21 ' and ' 2016-6-28 'There may be 10,000 data, then BUNIESSDATETIME2,BUNIESSSTATUS1, BUNIESSSTATUS2 filteringFinally, there is only one qualifying piece of data.The difference is that: at the beginning of the filter conditions, determine how many page queries to determine the initial criteria to meet the data, and then further filteringIf the data range that satisfies the query condition is determined relatively acc

beginning of the filter conditions, determine how many page queries to determine the initial criteria to meet the data, and then further filteringIf the data range that satisfies the query condition is determined relatively accurately at the very beginning, the data that satisfies the condition can be finally confirmed by a relatively small price.If the data range that satisfies the query condition is dete

Let's take a look at what bookmarks are:When the non-clustered index selected by the optimizer only contains a part of the query request fields, a lookup is required to retrieve other fields to meet the request. For a table with clustered indexes, it is a key lookup, and for a heap table it is an RID lookup ). This kind of search is-bookmarks search.Bookmarksearch reads data from the table based on the index row locator. Therefore, in addition to the

Let's take a look at what bookmarks are: When the non-clustered index selected by the optimizer only contains a part of the query request fields, a lookup is required to retrieve other fields to meet the request. For a table with clustered indexes, it is a key lookup, and for a heap table it is an RID lookup ). This kind of search is-bookmarks search. Bookmarksearch reads data from the table based on the index row locator. Therefore, in addition to t