mysql count if condition

SQL tuning is primarily about reducing the number of consistent gets and physical reads. COUNT (1) is compared with COUNT (*): If your datasheet does not have a primary key, then count (1) is faster than COUNT (*)If you have a primary key, the

The table structure is as follows: The code is as follows Copy Code Mysql> Show CREATE TABLE Userg;1. Row ***************************Table:userCreate table:create Table ' user ' (' ID ' int (a) unsigned not NULL

1. Official Documents:CountCOUNT(expr) [over_clause]Https://dev.mysql.com/doc/refman/8.0/en/group-by-functions.html#function_count1.1 Examples:Select Update_time,sid,group_concat (if (Age > ' 1 ', Tid, NULL)),count (DISTINCT if (age =1,tid,null)) as

MYSQL5.6.7-RC index condition pushdown indexed condition Push code interpretationHttp://jishu.zol.com.cn/4505.htmlMYSQL5.6.7-RC Index Condition pushdown code interpretation a-a+2013-08-07 11:10|Share to:Interested in the index condition Pushdown,

Translator: ye Jinrong (imysql # imysql.com), source: imysql.com, please reprint it. Cause: It is too slow to make count (*) Statistics on the innodb table, so try to see if you can hurry up. Symptom: Let's take a look at several test cases. 1. Test

The performance of the MySQL database is always the focus of discussion. The following describes the efficiency of the COUNT (*) in MySQL database optimization. I hope it will help you. In MySQL database optimization, COUNT (*) and COUNT (COL ):I

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

I just solved the Discuz he wrote for a friend! Plug-in problems, when talking about the efficiency of MySQL COUNT (*), the more I find it unclear, simply write it down and share it with you. I just solved the Discuz he wrote for a friend! Plug-in

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

Where Condition Query The code is as follows SELECT * FROM news where DATE (adddate) between ' 2011-04-20 '-INTERVAL 5 day and ' 2011-04-20 ' + INTERVAL 5 day SELECT * FROM news where DATE (adddate) in (' 2011-04-20 ', ' 2011-04-15 ', ' 2011-04-2