query optimization techniques in sql server

rstByQuery = mycommand. Execute ()I = 0Do While Not rstByQuery. EOFI = I + 1' number of records saved in IRstByQuery. MoveNextLoopMSFlexGrid1.Rows = I + 1 'dynamically sets the rows and columns of MSFlexGridMSFlexGrid1.Cols = rstByQuery. Fields. count + 1MSFlexGrid1.Row = 0For I = 0 To rstByQuery. Fields. count-1MSFlexGrid1.Col = I + 1MSFlexGrid1.Text = rstByQuery. Fields. Item (I). NameNext 'set the title of the first line and fill it with the domain nameI = 0RstByQuery. RequeryDo

Server clusters take advantage of the built-in cluster functions in Enterprise Edition of the Windows Server series. In fact, Windows Server 2003 is much better for clusters than Windows 2000 Advanced Server. To maximize the benefits you get from the cluster, you need the right hardware, which costs some. It is not eno

the pleasant parallel, enjoying the pleasure of parallel brings.　　It is similar to the function processing on the join condition, after calculating the result, save in a variable, write the variable in the join condition,Of course there may be other ways that I haven't thought of yet.Summarize:In this paper, a simple example demonstrates the suppressed behavior of parallel operations, illustrating the huge difference between parallel and serial performance on a cost-significant SQL.The

the batch query specified by the Plan handle in XML format. The plan specified by the scheduler handle can be in the cache or running state. Sys. dm_exec_query_stats: return the aggregate performance statistics of the cache query plan. Each query statement in the cache plan corresponds to a row in this view, and the row survival is associated with the plan itsel

To reduce the scope of the read operation, this article first looks at a simple select query and then introduces additional procedures related to performing the update operation. Finally, you will read that SQL Server uses the terminology and processes associated with the Restore tool when optimizing performance.relational and storage engines,

Tags: relative resolution time expression truncate log compare local tipsThis article summarizes 30 mysql Tens Big Data SQL query optimization techniques, especially for MySQL use in big data. 1. To optimize the query, avoid full-table scanning as far as possible, and first

Tags: SQL statement electronic win style SPAN different statement column DTS --Connect remote SQL or insert data with OPENROWSET --if only temporary access, you can directly use OPENROWSET --Query Example Select * from OpenRowset('SQLOLEDB' ,'SQL Server name';'User name

SQL server databases are the most widely used relational databases. However, in actual application, many databases need to be optimized. When the data volume is particularly large, we must rely on the optimization of our team's database. Such as creating indexes, table partitions, database shards, and table shards. This article summarizes some

logical reading of the statistical principle: why the results displayed in the unit is not page, nor K or KB. Sql server When you do the reading and writing, you run to a specific piece of code. Each time this code is called, Reads/write will add 1. So this value is larger than That statement must have done a lot of I/O, but not by this value to calculate the absolute number of I/O, this value reflects the

|+---------------------------------+-------+| 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 |+---------------

Introduction In SQL Server, each query finds the shortest path to achieve its goal. If the database only accepts one connection, only one query is executed at a time. Therefore, queries must be completed quickly and easily. However, most databases need to process multiple queries at the same time. These queries will n

= e.dept_no efficient Select D Ept_no, dept_name from DEPT D WHERE EXISTS (SELECT ' X ' from EMP E exists makes queries faster because the RDBMS core module returns the result immediately after the condition of the subquery is satisfied 13. Use Index to improve efficiencyAn index is a conceptual part of a table that is used to improve the efficiency of retrieving data. In fact, SQL Server us

Tuning Advisor call that file for analysis by SQLThe server provides index tuning recommendations. Adopt its Index index optimization section.4, but the above practices often do not run out of your needs, in the recent optimization process of high CPU utilization, but not at all I need to make the optimization recomme

Label:Many people don't know how SQL statements are executed in SQL Server, and they worry that the SQL statements they write will be misunderstood by SQL Server. Like what: Name=> 10000 and execution:

copy of the original table, but in fact each server has only one member table and a distributed partition view. The data location is transparent to the application. 11. Rebuild the index dbcc reindex, dbcc indexdefrag, shrink data and log dbcc shrinkdb, and dbcc shrinkfile. set automatic log shrinking. for large databases, do not set Automatic database growth, which will reduce the server performance. The

. Efficiency will therefore be improved. It is important to note that the UNION all will output the same record in the two result set repeatedly. So you still have to analyze the feasibility of using union all from the business requirements. The UNION will sort the result set, which will use the memory of the sort_area_size. The optimization of this memory is also very important. The following SQL can be us

. Connect the temporary table to the vendor table, output the result to a temporary table, and sort by part_num:Select pv_by_vn, * vendor. vendor_num from pv_by_vn, vendorWhere pv_by_vn.vendor_num = vendor. vendor_numOrder by pv_by_vn.part_numInto TMP pvvn_by_pnDrop table pv_by_vnThis query reads pv_by_vn (50 pages) and uses indexes to access the vendor table for 15 thousand times. However, due to the vendor_num order, in fact, the vendor table is rea

1. IntroductionIn the early stage of application system development, because the database data is relatively small, for querying SQL statements, the use of indexes and the writing of complex views can not understand the performance of the SQL statement of various ways, but the application system in practice, with the data in the database increases, The response speed of the system is one of the most importa

methods of emptying SQL Server log files from the 10thOne way: Empty the log.1. Open Query Analyzer, enter command dump TRANSACTION database name with NO_LOG2. Open Enterprise Manager again--right click on the database you want to compress--all tasks--shrink the database--Shrink the file--Select the log file--in the contraction mode to choose to shrink to XXM, h

Tags: common function reference. com diff func Ted which interface comparisonUsing SQL Server for a long time, today especially want to summarize, is a review it!Common functions:1. ISNULL (columnName, ")First determine if the field is empty, if it is empty, return '; Otherwise, the value of the field is returned.2. DATEDIFF (datepart,startdate,enddate)No wordy, direct reference link3.Useful statements:1. S