postgresql query optimization tips

like:SELECT [Column1],[column2],.... From [TABLE] ORDER by [sort] LIMIT [offset],[limit];This SQL statement optimization is relatively simple and can be indexed on the [Sort] field.(2). WHERE + ORDER by + limit combination index optimization, shaped like:SELECT [Column1],[column2],.... From [TABLE] WHERE [COLUMNX] = [VALUE] ORDER by [sort] LIMIT [offset],[limit];This statement, if you still use the first e

Five practical tips for MySQL Query Optimization, This article summarizes and analyzes the MySQL query optimization techniques. We will share this with you for your reference. The details are as follows: Anyone familiar with SQL statements knows that if you want to perform o

50 tips for optimizing query: (see which one is suitable for you) 1. Place data, logs, and indexes on different I/O devices to increase the reading speed. In the past, tempdb can be placed on raid0, which is not supported by SQL2000. The larger the data size (size), the more important it is to increase I/O. 2. vertically and horizontally split the table to reduce the table size (sp_spaceuse) 3. upgrade hard

with indexes, it can only search the data in the table directly. For example: The Select ID from the employee WHERE ID! = "B%" Optimizer will not be able to determine the number of rows in the fatal row by index, so you need to search all rows of the table.In the in statement can use the EXISTS statement instead of the exists. four . Rational use of exists,not exists clauses Five , you can use between do not use in Six , can use distinct without GROUP by Seven , try not to use the SELECT INTO

Summary: practical tips for MySQL table creation and query optimization bitsCN.com Summary: practical tips for MySQL table creation and query optimization The MySQL table creation stage is a very important step. the quality and

to explicitly delete all temporary tables 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. Before using a cursor-based method or temporal table method, you should first look for a set-based solution to solve the problem, and the set-bas

Summary some useful tips for MySQL table creation and query optimization bitsCN.com The MySQL table creation stage is a very important step. the quality and advantages of the table structure directly affect the subsequent management and maintenance, I will share some practical tips to summarize my accumulation of MySQL

, 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. Before using a cursor-based method or temporal table method, you should first look for a set-based solution to solve the problem, and the set-based approach is generally more efficient.27. As with temporary tables, cursors are not unusable. Using Fast_forward cursors

30 SQL query optimization tips for mysql with tens of millions of big data, mysqlsql 1. To optimize 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 null value determination on the field in the where clause. Otherwise, the engine

overwriting if the cursor is manipulating more than 10,000 rows of data.26. Before using a cursor-based method or temporal table method, you should first look for a set-based solution to solve the problem, and the set-based approach is generally more efficient.27. As with temporary tables, cursors are not unusable. Using Fast_forward cursors on small datasets is often preferable to other progressive processing methods, especially if you must reference several tables to obtain the required data.

The MySQL table creation stage is a very important step. The quality and advantages of the table structure directly affect the subsequent management and maintenance, I will share some practical tips to summarize my accumulation of MySQL tabulation and MySQL query optimization before going to work tomorrow. Tip 1: add time and update time for redundant data table