mysql select count

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

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

Tested under MySQL 5.6.MyISAM Engine:When creating a data table, MySQL generates 3 files, respectively (table: Test):TEST.FRM, Test. MYD, Test. Myi file,TEST.FRM is the table structure, Test.myd is the file that holds the data, Test.myi is the file

  1. select count (*) FROM tablename is the optimal choice under any circumstances; 2. Minimize select count (*) FROM tablename where col = 'value' queries; 3. prevent the appearance of select count (COL) FROM tablename.     COUNT (*) and COUNT (COL)

In MySQL found_rows () and COUNT (*) can be recorded, if all the same why there are two such functions, I would like to introduce the Select Found_rows () and the Count (*) Usage differenceIt is often possible to return rows with limit restrictions

I. User table information     Ii. Conclusion   Use the query statement: Select count (1) from user; Use the explain statement to check whether the statement is indexed. the following result shows the query time of the statement. Data Volume query

Mysql count details and function instance code, mysqlcount Mysql count details The count function is a function used to count records in tables or arrays. The following describes how to use the count function in mysql. Count (*) returns the number

In MySQL found_rows () and COUNT (*) can be recorded, if all the same why there are two such functions, I would like to introduce the Select Found_rows () and the Count (*) Usage differenceIt is often possible to return rows with limit restrictions

1. Test Environment OS: LinuxDB: mysql-5.5.18Table: innodb Storage Engine The table is defined as follows: 2. test scenario and analysis [number of group_message records in the statistical table] (1) select count (*) Method (2) select count