Get data randomly in MySQL

Because of the need to probably study the MySQL random extraction implementation method.

The current method used:

　　

SELECT    *  from     tablenameORDER by    RAND  1

Implementation principle:

Using ORDER by RAND () to disrupt the sorting of data, limit limits the number of bars to get the data.

Disadvantages:

Low efficiency. When a large data volume is retrieved, the retrieval time is increased. A library of more than 150,000, query 5 data, incredibly more than 8 seconds.

The official manual shows that rand () is executed several times in the ORDER BY clause and is naturally inefficient.

Get data randomly in MySQL