postgresql query optimization tips

Label:About the effect of SQL condition matching on execution efficiency test First, create a scalar functionCreate function Ff_test ()returns intAsBeginDECLARE @i int=0while (@iSet @i+=1Return @iEnd Next, select a random table, where you use the business table Mt_delegate Observe the following two types of situations 1. Select * from mt_delegate where procid=-1 or dbo.ff_test () >10000 2. Select * from Mt_delegate where dbo.ff_test () >10000 or Procid=-1 The result is that the order of the Wher

38 PHP encoding optimization acceleration techniques. 1. try to use a large number of PHP built-in functions. 2. echo is faster than print. 3. do not subscribe too many methods. think carefully about the code you actually intend to reuse? 4. execute the for loop. 1. try to use a large number of PHP built-in functions. 2. echo is faster than print. 3. do not subscribe too many methods. think carefully about the code you actually intend to reuse? 4. de

there is no need to optimize unless you feel it can make your code easier to read (and Final,static,static final is more true)Frequently measuredBefore you start optimization, make sure you have some problems to solve. Make sure you can measure your existing performance accurately, otherwise you won't be able to measure the benefits of the alternatives you're trying toEach statement in this article has benchmarks, and the source code for the benchmar

MySQL is a powerful open-source database. With more and more database-driven applications, people have been pushing MySQL to its limits. Here are 101 tips for adjusting and optimizing MySQL installation. Some of the techniques are specific to the installation environment, but these ideas are generic. I've divided them into several categories to help you master more of the tuning and optimization techniques

MySQL Performance Optimization Tips help your database bitsCN.com you have completed your brand new applications, everything works like a charm. To use your network. Everyone is happy. Then, suddenly, an explosive user killed your MySQL server and your website was closed. What's wrong? How can you stop it? The following are some tips for MySQL performance

Original addressMySQL is a powerful open source relational database management system (RDBMS). It was posted on 1995 (20 ago). It uses Structured Query Language (SQL), which may be the most popular choice in database content management. The latest MySQL version is 5.6.25, released on May 29, 2015.An interesting fact about MySQL is that its name comes from the daughter "My" of Michael Widenius (the founder of MySQL). Although there are many interesting

to their own site SEO optimization, The following is a simple introduction about Taobao SEO optimization tips! 　　One: The internal optimization of the website In fact, want to Taobao to promote the success of the first of their own internal strength to a certain degree of heat, which will involve SEO

Java performance optimization tips I. General1.1 create a class instance without the New Keyword1.2 use non-blocking I/O1.3 usage exceptions with caution1.4 do not reinitialize the variable1.5 specify the final modifier of the class as much as possible1.6 use local variables whenever possible1.7 multiplication and divisionIi. J2EE2.1 use a buffer flag2.2 always access the Entity Bean through the session bea

Hive optimization tips-How to Write HQL I. Hive join Optimization1. try to place the small table on the left of join. The hive-0.12.0 we use here is automatically converted. This means that the small table is automatically loaded into the memory and the map side join is executed (with good performance ), this is done by the hive parameter. auto. convert. join = true and hive. smalltable. filesize = 25000000

character as an argument, and the parameter length is not too long, consider writing an extra paragraph of substitution code so that each pass parameter is a character, rather than writing a single line of code to accept the array as a query and replacement parameter. 13. Using the Select Branch statement (ie, switch case) is better than using multiple if,else if statements. 14. Using the @ Block error message is very inefficient. 15. Open the Apache

Label: When using the group by group query, the default grouping is also sorted (using Filesort) and may slow down. Workaround: Add order by NULL to not sort it Select * from Group by Empno orderbynull; In some cases, you can use a connection to replace a subquery. Because using Join,mysql does not require the creation of temporary tables in memory Select * from where dept.deptno=[ simple handling mode ] Select*