Read about sql query optimization tips, The latest news, videos, and discussion topics about sql query optimization tips from alibabacloud.com
the merge do not contain duplicate data, use Union all, as shown below:Select * From test_union1Union allSelect * From test_union2 There are two basic rules for query result sets using union: 1. The columns and columns in all queries must be in the same order. 2. Data type must be compatible Database Query Optimization: 1. To optimize the
Tags: store style col MySQL share picture lob Div using indexfirst, MySQL's slow query log opening and storage 1, check whether the SQL records that do not use the index to the slow query log, view the log_queries_not_using_indexes variable; like "Log_queries_%" Results: If the value of the query is off, it indicat
SQL Server multi-Table query optimization solution highlights, sqlserver The multi-Table query optimization solution of SQL Server is what we will introduce in this article. We provide the opt
This section of this article will cover MySQL and may not be available in other databases. This section only discusses database structure design, and other content of query optimization is to be continued.Database design and use is a necessary basic skill for web development programmers, and it is very important for the project to have a reasonable data structure and SQ
after each statement that executes the stored procedure and trigger. 29. Try to avoid large transaction operation and improve the system concurrency ability. 30. Try to avoid the return of large data to the client, if the amount of data is too large, should consider whether the corresponding demand is reasonable. Besides, friends, if you have to use a query like '%a% ' It is recommended that you do a full-text index of the table, originally like
tables are explicitly deleted at the end of the stored procedure, TRUNCATE table first, and then drop table, 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, you should look for a set-based solution to solve the problem before using a cursor-based method or a temporary table method, which is often more efficient t
by Cust.nameThen query in the view in the following way:SELECT * from V_cust_rcvlbesWHERE postcode> "98000"The rows in the view are less than the rows in the primary table, and the physical order is the required order, reducing the disk I/O, so checkThe workload 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
In general, Oracle databases operate more efficiently than SQL Server databases in large data environments. From the query optimization alone, the two are quite different. Below, the author of the database query optimization of the difference to do a description, if there is
2005 provides the INCLUDE parameter in the Create Index statement, add other fields of the data table unrelated to the key-value column to the leaf layer of the non-clustered index to expand the non-clustered index function. However, these fields are not sorted and other additional maintenance actions are not performed. When querying, you can obtain all relevant data only by reading the index structure, without accessing the table or clustered index data, thus reducing disk I/O operations, redu
Tags: server ASI How much data query size optimization way up and down no1. When you need to query all the data in the tableCompare the following three types of query statements:Suppose the data table is BasicMsg20170401, there are 17 columns, and the number of data bars is 2.84 million(1) SELECT * from BasicMsg2017040
The optimization scheme of SQL Server Multi-table query is the main content of this article, we give the optimization scheme and specific optimization examples, then let us take a look at this part of the content. 1. Execution path This feature of Oracle greatly improves t
In our usual SQL query, in fact, we have a lot to pay attention to the principle, since the implementation of SQL query optimization , this article will introduce 30 query optimization
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?view=sql
. In the third step, the sub-bar checks to find out which table query is slow, or which condition causes the query to be slow. The fourth step, with the SQL execution plan, this because they are not good at looking at execution plan, can only try to avoid full table scan, early limit the scope of SQL data filtering. Th
tried to do this using the following SQL (for the sake of comparison, the columns of both tables are output): SELECT stu.name, stu.class, s.name, s.score FROM student AS stu LEFT JOIN score AS s ON stu.name = s.name AND stu.class = ‘A‘ At first glance, there seems to be no problem, but also left the connection and on the condition of the increase in class restrictions, in fact, the results appear in Class B classma
1. UseProgramTo minimize the number of accesses to the database. By searching for parameters, You can minimize the number of rows accessed to the table and the result set, thus reducing the network burden; separate operations should be processed separately to improve the response speed each time. When using SQL in the data window, try to place the indexes in the first column selected;AlgorithmThe structure should be as simple as possible; During the
. Please submit the query again, and do not specify any prompts in the query, or use set forceplan.Check the following documents, that is, this statement does not support option (merge join );Switch to not exists and try again to see if the effect will be better.Select * From tablea where not exists (select 1 from tableb where tablea. ID = tableb. ID)After passing the test, it is found that the speed is imp
First, we will compare two paging SQL statements. For example, the news table has 0.15 million records, NewsTypeId10 has 90 thousand records, and NewsTypeID10 is currently queried. Which SQL statement will be considered as highly efficient? First, compare the two paging SQL statements. Assume that the news table has 0.15 million records, NewsTypeId = 10 has 90 th
In the actual development often encounter the same keyword need to multi-field fuzzy query, such as a user table in the Input keyword query may be to the user name, user name, contact phone fields such as fuzzy queryIf written as: where UserName like '% ' keyword% ' or fullName as '% ' keyword% ' or mobile kind '% keyword% ' This way will result in very low performance, hundreds of thousands of data may be
return any result sets, but consumes system resources and should be changed to this: CREATE TABLE #t (...) 13, a lot of times with exists instead of in is a good choice: Select num from a where num in (select num from B) Replace with the following statement: Select num from a where exists (select 1 from b where num=a.num) 14, not all indexes are valid for the query, SQL is based on the data in the table to
Start building with 50+ products and up to 12 months usage for Elastic Compute Service
1 on 1 presale consultation
24/7 Technical Support 6 Free Tickets per Quarter Faster Response
Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.
A comprehensive suite of global cloud computing services to power your business
Payment Methods We Support
