sum with condition mysql

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

The calculation of some numbers is not difficult, the whole is to cultivate the logic of self-awareness, logic clear, the code naturally know that the overall training of their own logic, one is from the user perspective, one from the product

Tag: The code filtering process contains the activity requirements record Lin andThere was a 2-day outage two days ago.Data requirements:1. Event Date 11.8-11.10 Order2, a single order to buy a class B products to meet the 68 yuan, and 3 consecutive

##############################################################################################Data import: Store the contents of the system files in the table of the databaseCommand:Load data infile "directory/file" into table name fields terminated

Recently in the company to do projects, involving the development of statistical reports related to the task, due to the relatively large amount of data, the query before writing query 500,000 data about 10 seconds to look like, later through the

Mysql and Oracle use the rollup function to complete row and column statistics ??? Yesterday, I suddenly saw in a blog that Mysql also had the rollup function. The original blog post used rollup for row and column statistics. The original blog post

Count () differs from sum () in MySQLFirst, create a table to illustrate the problem create table ' result ' (' name ' varchar () default NULL, ' subject ' varchar () default NULL, ' Score ' tinyint ( 4) Default NULL) Engine=myisam default

Slow sql: Queries that run longer than a given time range are called slow queries.How do I record slow sql in MySQL?A: You can set the following information in MY.CNF: [Mysqld] ; Enable the slow query log, default

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

When does mutex need condition variable?Assume that there is a shared resource sum, and the associated mutex is lock_s. assume that the sum operation of each thread is very simple and irrelevant to the sum State. For example, it is only sum ++. only