postgresql query optimization tips

original state, cannot be replaced by the picture, this is to tell the CDN server this picture has changed, need CDN re-read, not read cache, When you add a version number, the image changes to the newly replaced image.6, CSS, JS compression problem:Here's how:Using the program, the page all JS merged into 1 JS and compression, CSS the same.Reason for adjustment:The advantage of this is to reduce the number of browser parsing JS and CSS, increase the resolution speed, make the website access sp

;//retrieving the first 5 records lines MySQL's limit brings great convenience to paging, but when the amount of data is large, limit performance drops sharply. also take 10 data, the following two sentences are not a number of levels. 10000,0,ten Instead of using limit directly, you first get the ID of offset and then use the limit size directly to get the data. According to his data, it is significantly better to use limit directly.Here I use the data in two different situations

= t.uid GROUP BY ps.uid ORDER BY credits DESC LIMIT 0 , 50 For each player, find the player number, name, and number of the player that is fined, but only for those who have at least two fines. For more compact queries, place a subquery in the from clause. SQL code SELECT PLAYERNO,NAME,NUMBER FROM (SELECT PLAYERNO,NAME, (SELECT COUNT(*) FROM PENALTIES WHERE PENALTIES.PLAYERNO = PLAYERS.PLAYERNO) AS NUMBER FROM PLYERS) AS PN WHERE NUMBER>=2 The subque

,player_idfrom link where player_id=‘15298635‘The number of records to be queried below 100, most of them only dozens of records, I can in the code in the query results will be traversed once to judge. I don't know how fast it is!Let's look at the following example:select * from browser where device_id=‘52‘ AND created>=‘1513735322‘ order by id descI just want to check the data for a certain time in the table. It's a big problem!createdThe field is a

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 only add a series of values after the in statem

For a detailed explanation of the page, see http://blog.csdn.net/u011225629/article/details/46775947View Code Print 1 SELECT * FROM table ORDER by ID LIMIT 1000, 10;The above SQL statements in principle and in the actual operation is not a problem, but when the table data volume reaches more than hundreds of thousands of of the time, the above statement executes once, it may take a few seconds, and when the number of pages, the more time to execute the longer, This time we need to find a faster

SQL optimization tips and guidelines To optimize queries and avoid full table scanning, you should first consider creating an index on the columns involved in where and order. Try to avoid null value determination on the field in the where clause. Otherwise, the engine will discard the index and perform full table scan. select id from t where num is null It is best NOT to leave NULL for the database and try

For a detailed explanation of the pagination, see http://blog.csdn.net/u011225629/article/details/46775947View Code Print 1 SELECT * FROM table ORDER by ID LIMIT 1000, 10;There is no problem with the above SQL statements in principle and in actual operation, but when the data volume of table tables reaches more than hundreds of thousands of. The above statement runs once and may take a few minutes to run, and the longer the page is, the more time it will run. This time we need to find a faster w

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 tricks are specific to the installation environment, but these ideas are generic. I've divided them into several categories to help you learn more about MySQL's tuning and optimization skills.

How to optimize the performance of Python is the main problem discussed in this paper. This article will cover the common code optimization methods, the use of performance optimization tools and how to diagnose the code performance bottlenecks, and so on, I hope you can give a reference to Python developers. Common tips for Python code

keyword combination. The execution of right join is similar to that of left join, but the role of the table is the opposite. The order in which the join optimizer calculates the table to be joined. The forced read sequence of left join and STRAIGHT_JOIN can help the JOIN optimizer to work faster, because fewer table exchanges are checked. Note that if the following type of query is executed, MySQL performs full scan B, because LEFT JOIN forces it to

MySQL's 101 tuning and optimization tips: bitsCN. comMySQL is a powerful open-source database. With more and more database-driven applications, people have been pushing MySQL to its limit. Here are 101 Tips for adjusting and optimizing MySQL installation. Some tips are applicable to specific installation environments,

This article mainly introduces the efficiency analysis and optimization of Mysql multi-table joint query. For more information, see the following code: SELECT column_name FROM table1 LEFT [OUTER] JOIN table2 ON table1.column = table2.columnB. RIGHT [OUTER] JOIN: The difference between RIGHT and left join is that in addition to displaying results that meet the connection conditions, you also need to displa

1: When multiple table associations are used, the multiple where statement minimizes the result set of a single table, uses aggregate functions to summarize the result set, and then associates with other tables to minimize the amount of result set data 2: You should consider the possibility of using a right connection when you are associating two tables. To improve query speed3: Use where instead of having , where is used to filter rows, and having is

How to optimize the performance of Python is the main problem discussed in this paper. This article will cover common code optimization methods, the use of performance optimization tools and how to diagnose the performance bottlenecks of the code, and so on, hoping to give Python developers a certain reference. Common tips for Python code

Optimization tips for slow subquery efficiency of mysql in statements, mysql examples The table structure is as follows. There are only 690 articles. Article table article (id, title, content) label table tag (tid, tag_name) label intermediate table article_tag (id, tag_id, article_id) The tid of a tag is 135, and the list of articles whose tid is 135 is queried. In the first article, we used the following

MySQL is a powerful open-source database. With more and more database-driven applications, people have been pushing MySQL to its limit. Here are 100 tips for adjusting and optimizing MySQL installation. Some tips are applicable to specific installation environments, but these ideas are common. I have already divided them into several categories to help you master more MySQL adjustment and

minimum.For concatenation of strings, use StringBuffer instead of string.Do not declare temporary variables in the loop, do not catch exceptions in loops.If there is no requirement for thread safety, try to use a thread-unsafe collection object.Using a Collection object, you can set the initial size in the construction method if you know its size beforehand.File read operations need to use the cache class to close the file in a timely manner.Caution with exceptions, using exceptions can cause p

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

Label: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 techn