mysql count if condition

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In MySQL, COUNT (1) is compared to count (*)

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

Usage differences for COUNT (ID) count (1) count (*) in MySQL

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

Mysql count (1) Group_concat Advanced usage (count filter condition, GROUP_CONCAT filter condition)

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 interpretation

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,

Optimization of innodb table count () in mysql

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

MySQL database Optimization-COUNT (*) Efficiency

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

Learn MySQL (UP)

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

Mysql Optimization-COUNT (*) Efficiency Analysis

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

With Count (*) or count (column name) | | Count () differs from sum () in MySQL

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

MySQL condition query if case usage

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

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