sql query optimization tips

achievement of the same students with different course grades.43. Check the top two of the best results for each door44. The number of students enrolled in each course (more than 10 participants are counted). Require the output of the course number and the number of elective, query results in descending order of numbers, query results in descending order of numbers, if the number is the same, in ascending

, 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 writing of T-SQL is very important. The following lists common points: fi

MySql SQL optimization tips and mysqlsql tips One day I found that the execution speed of an SQL statement with inner join was not very slow (0.1-0.2), but it did not reach the ideal speed. The two tables are associated, and the associated fields are all primary keys. The qu

SQL Server query performance optimization analysis transactions and locks (I) SQL Server query performance optimization analysis transactions and locks (ii) SQL Server

Three common causes of poor SQL query statement performance and Optimization Methods 1. Reasons for affecting SQL Performance There are many factors that affect SQL performance, such as incorrect initialization parameter settings and inaccurate system statistics imported, th

Optimization of ms SQL Server Query Author: xmllover 2007-11-29 There are many reasons for slow query speed. 1. No index or no index is used (this is the most common problem of slow query and is a defect in programming)2. Low I/O throughput, resulting in a bottleneck effect.

I have had 10 SQL optimization experiences in the past, but I still feel that it is not specific enough. Now I want to add some specific problems I encountered during my work. Today, let's talk about the situation of select... where... in. Sometimes there are many discrete values in our query conditions, such as the id value of a table. In this case, we can on

Label:From: SQL Server Query performance optimization-heap table, fragmentation, and index (i) SQL Server Query performance optimization-heap table, fragmentation, and index (ii) SQL Se

. 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

that there are some queries that are not expected (the so-called "expected query", that is, the user believes that the query results inconsistent is also reasonable, such as orders in order to change the status of orders in order to lead to inconsistent results and so on), because "dirty read" caused by "dirty data" inconsistent query results before and after Tw

When querying database records using SQL statements, there are many different ways to query the same content.Still, although you can get the same results using a variety of methods, if you use a different approach, the execution benefits are quite different. Therefore, we have to consider carefully, if you want to query the same results, which statement to use, t

Label:In the original: Remember the SQL query optimization of a bitter forceRecently in the maintenance of the company project, the need to load a page, a total load of more than 4,000 data, it takes 35 seconds, if the data grew to 40,000, I estimate a few minutes can not be confused. Lying trough, to me is the user's words estimate can not stand, while idle of n

SQL Server query performance optimization analysis transactions and locks (2 ). Step 1: Execute Example 2 and Example 3 code in the query analyzer. (This is the example in the previous article SQLSERVER query performance optimization