MySQL random number, MySQ random data, MySQ random data query, and MySQ random data update

 

This article implements the random numbers of MySQL, random data selection by MySQ, random data query by MySQ, and random data update by MySQ.

MySQ Random Data Query

I have discussed this issue in the group before. It is quite interesting. mysql syntax is really fun. they all wanted to use PHP to implement random queries, but retrieving multiple entries seemed to require more than two queries. after reading the manual, find the following statement to complete the task.

SELECT * FROM table_name order by rand () LIMIT 5;

 

The rand () function of MySQL is described in the Manual as follows:

RAND ()

RAND (N)

Returns a random floating point value ranging from 0 to 1.0. If an integer parameter N is specified, it is used as a seed value.

About the efficiency of MySQL rand () function, you can refer to the MySQL Order By Rand () Efficiency: http://www.bkjia.com/database/201111/112544.html

 

Actual Effect

Mysql> select RAND ();

-> 0.5925

Mysql> select RAND (20 );

-> 0.1811

Mysql> select RAND (20 );

-> 0.1811

Mysql> select RAND ();

-> 0.2079

Mysql> select RAND ();

-> 0.7888

Random update of MySQ data

How can I write a statement to update hundreds of MYSQL Data Records!

To test the MYSQL database, there is a database with tens of thousands of data records. How to Write a PHP file and update several hundred pieces of information each time? I write a loop to update one piece of information at a time, in this way, I can use WHILE to write data. How can I write an update like 100 data records?

The correct answer is: UPDATE cdb_posts SET views = rand ();

In the insert command, rand () is used in value (). Note whether the field width is sufficient to always think that mysql randomly queries several pieces of data.

SELECT * FROM 'table' order by rand () LIMIT 5

 

From Hurry's column