identify poor performance in sql server

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

than the number of rows of data The statements and data used in the example are used only as demos, the actual development application is more complex than the sample data, the same query in different circumstances may produce the opposite result, how to apply well is mainly in our personal understanding and understanding, hope to see this article friends can deepen some understanding of the index and understanding , and get rid of the error of index and develop high

With the growth of time, the company's database will be more and more, query speed will be more and more slow. Open the database to see hundreds of thousands of of data, the query is inevitable not waste time. To improve SQL query effectiveness, you will generally want to build indexes (index) as the first consideration. In fact, in addition to the establishment of the index, when we are in the SQL command

ExecuteScalar method to retrieve a single value (for example, an ID number) from the database ). This operation requires less code than executing the operations required to generate a single value for the returned data using the ExecuteReader method.You only need to update the data using ExecuteNonQuery. Use ExecuteScalar to query a single value. Ii. SqlDataRead and Dataset SelectionSqldataread advantages: fast data reading. If you do not need to process the returned data in large quantities, w

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

database administrators to test to confirm the obvious functionality, but a second person should be scheduled to test. If you don't have a budget to ask a full-time or part-time tester, consider having the development team check in with each other. If you have a budget for testers, then let your team add load to the application. Streamline the load test process When an application is published as a product, identify some of the factors that work wi

not very useful because the connection command is not included in the query, but this information is useful if the query contains one or more connections.The scan count value for a table outside a loop is 1, but for a table within a loop, its value is the number of cycles. As you can imagine, for a table within a loop, the smaller the value of its scanner, the less resources it uses, and the higher the performance of the query. Therefore, when adjust

rows reserved data index_size unused TB_WCB 9439661 317208 kb 167168 KB 149872 KB 168 KB */ we found that the size before index compression was 329M. And after compression is 149M, the compression ratio is 45%. The effect is also very obvious. Summarize: Compression through tables and indexes. We can reduce the disk space occupied by the table, this is only part of it, and more importantly, reading the same amount of data, just need to read less data pages,

Brief introduction In SQL Server, data is stored on a page. When you add a clustered index to a table, SQL Server searches for the data by using the columns of the clustered index as the keyword. Therefore, the impact on performance of the selection of clustered indexes bec

not fully covered, at least to explain a part. Above we get the results to view the execution time, now let's look at both the query execution plan. Select COALESCE (select MAX (index_id) from sys.indexes WHERE [object_id] = t.[object_id]), 0) from sys.tables as T; select ISNULL (SELECT MAX (index_id) from sys.indexes WHERE [object_id] = t.[object_id]), 0) from sys.tables as T; The above may not be accurate, but also related to hardware configuration, it is possible to coale

Tags: des style blog http color io os ar strongOriginal: 5. SQL Server database performance monitoring-current requestFor systems running on-line, current database performance monitoring typically monitors the following points:(1) Whether there is obstruction (Blocking);(2) whether there is waiting (waiting), blocking

Label:Original: SQL Server database Performance tuning tipsThe reasons for the slow query are many, and the following are common: 1. No index or index is not used; 2, I/O throughput is small, forming a bottleneck effect; 3, insufficient memory; 4, the network speed is slow; 5, the amount of data queried is too large; 6, lock or deadlock; 7, the return of unnecess

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

Tags: performance optimization for SQL Server administrator-required skillsPerformance optimizations for SQL Server administrator-required skillsSQL Server is one of the essential services of the enterprise, so it is a great chall