if else statement in mysql select query

MySQL常用指令，java，php程序员，数据库工程师必备。程序员小冰常用资料整理MySQL common commands (for reference)The most common display commands are:1. Display the list of databases.show databases;2. Display the data table in the library:Use MySQL;Show tables;3, display the

Concrete Example 1. PHP Server ComponentsFor beginners, it is recommended to use the integrated server component, which already includes PHP, Apache, Mysql and other services, eliminating the time spent by developers in the tedious configuration

Case has two formats. Simple case function and case search function.--Simple Case functionCase SexWhen ' 1 ' Then ' men 'When ' 2 ' then ' women 'Else ' other ' END--case search functioncase If sex = ' 1 ' Then ' man 'When sex = ' 2 ' Then ' women

Case has two formats. Simple case function and case search function.--Simple Case functionCase SexWhen ' 1 ' Then ' men 'When ' 2 ' then ' women 'Else ' other ' END--case search functioncase If sex = ' 1 ' Then ' man 'When sex = ' 2 ' Then ' women

Welcome to the Linux community forum and interact with 2 million technical staff to access Mysql's DQL query statement 1. query all columns-query all records of the student table (ROW) select * from student -- Query with conditions select * from

18.2.1 MySQL server has gone away errors related to Lost connection to server during query. The most common cause of the MySQL server has gone away error is that the server times out and closes the connection. By default, if nothing happens, the

MySQL character set ultimate solution [posting]   MySQL, an open-source database, has always been the first choice for small and medium-sized enterprises to build Web applications. In particular, It is a golden partner to cooperate with PHP and

Nesting Queries Poor optimization As I mentioned above, a table query is more efficient than a nested query, regardless of the particular situation. Although the two queries express the same meaning, although your plan is to tell the server what to

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

MySQL index details, MySQL index detailsI. Introduction to index basics 1.1 In MySQL, indexes are also called keys. They are a data structure that the storage engine uses to quickly find records. Indexes are critical to good performance. Especially