mysql two selects in one query

For high-performance database operation, it is not enough to design the optimal library table structure, and to establish the best index, but also need reasonable design query. If the query is poorly written, high performance cannot be achieved even

In the practical application, often need to implement in a query statement to display more than one table of data, this is called a multiple table data record connection query, referred to the next year will be the query. When you implement a

Transferred from: http://www.cnblogs.com/likwo/archive/2010/04/16/1713282.htmlQuery Day:SELECT * FROM table where to_days (column_time) = To_days (now ());SELECT * FROM table where date (column_time) = Curdate ();Query one week:SELECT * FROM table

In-depth analysis of explain for MySQL Query optimization MySQLexplain BitsCN.com When analyzing query performance, it is also useful to consider the EXPLAIN keyword. The EXPLAIN keyword is generally placed before the SELECT query statement to

1, Connection MySQL format: mysql-h host address-u user name-P user Password1. Connect to MySQL on this machine. First open the DOS window, then enter the directory Mysql\bin, and then type the command Mysql-u root-p, enter after the prompt you to

This article mainly introduces the analysis on English letters and lowercase letters in MySQL. The author has conducted experiments from multiple perspectives. if you need a friend, refer to the mysql database for query, sometimes English letters

In the manual, the query optimizer provides an overview of the tasks of the query optimizer, which is the best solution for discovering the execution of SQL queries. Most query optimizers, including the MySQL query optimizer, always search for the

This article transferred from: HTTPS://WWW.TUICOOL.COM/WX/2EMBFMQObjectiveTalking about MySQL query optimization, I believe you have a collection of artifice: You cannot use SELECT *, do not use null fields, reasonably create an index, select the

Install mysql in centos5.8 1. Install mysql yum Source Download the rpminstallation package of mysql's latest yumsource from http://dev.mysql.com/downloads/repo/yum/   wget http://repo.mysql.com//mysql57-community-release-el6-9.noarch.rpm Use yum

Query performance optimizationWhy is the query slower? The life cycle of a query can be roughly in order: from the client to the server, then parse on the server, generate execution plans, execute, and return results to the client. In the execution