mysql count where condition

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

The table structure is as follows:Mysql> Show CREATE TABLE user\g;*************************** 1. Row *************************** table:usercreate table:create Table ' user ' ( ' id ' int (ten) unsigned not NULL AUTO _increment, ' name '

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

MySQL Association leftjoin condition on and where different bitsCN.com I encountered a problem about the difference between on and where in left join at work today. I don't know if I can use where in left join. I asked my colleagues to know! This

Recently, in the background of a website to add a series of statistical functions, encountered a lot of conditions to be counted by the condition. Try several methods, the following summary records, for your reference.Problem descriptionTo make the

In MySQL query, sometimes the business complex, have to write multi-table query, many of the early apes like to write subqueries, because the subquery is easy to understand, not prone to problems, but the efficiency of sub-query is not as related to

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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

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