The following articles mainly describe the application of MySQL random query data, MySQL random update data, and the actual application code of MySQL random query data and MySQL random update data, the following is the description of the main content of the article. I hope you will gain some benefits.
The following articles mainly describe the application of MySQL random query data, MySQL random update data, and the actual application code of MySQL random query data and MySQL random update data, the following is the description of the main content of the article. I hope you will gain some benefits.
MySQL random query data
I have discussed this issue in the group before. It is quite interesting. mySQLl 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.
The Code is as follows:
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 "MySQLL Order By Rand () Efficiency": http://www.phpq.net/MySQLl/MySQLl-order-by-rand.html
Actual Effect
The Code is as follows:
MySQLl> select RAND ();
-> 0.5925
MySQLl> select RAND (20 );
-> 0.1811
MySQLl> select RAND (20 );
-> 0.1811
MySQLl> select RAND ();
-> 0.2079
MySQLl> select RAND ();
-> 0.7888
MySQL random update data
How can I write a statement to update several hundred pieces of MySQLL data!
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:
The Code is as follows:
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.
The Code is as follows:
SELECT * FROM 'table' order by rand () LIMIT 5
The above content is related to the random query data of MySQLL and the random update data of MySQL. We hope you will have some gains.
