rand value

MySQL Error injection principle analysis (count (), Rand (), GROUP by)0x00 questionshave been using the MySQL Database error injection method, but why the error?Baidu Google know a bit, found that everyone is the official website of the conclusion

The RAND () Optimization Method for MySQL optimization and the rand Method for mysql Optimization As we all know, in MySQL, if order by rand () is used directly, the efficiency is very poor because it will be executed multiple times. In fact, this

See Summer snow on the winter of Rand () and srand () produce random number of summary, very good, study, and then have Baidu other people's results, the system summarizes. This article turns from Summer snow winter:

Http://hi.baidu.com/jkxtu1984/blog/item/d5d1f1c6e5ac461d9d163dec.html The standard library (included in ) provides two functions to help generate pseudo-random numbers: Function 1: int rand (void );Returns a random integer between [seed, rand_max (0

The C language uses the rand () function to implement random (int m), randrandom The rand () function is a real random number generator, and srand () sets the random number seed for rand. If you did not call srand () before calling rand () for the

This article mainly introduces the RAND () optimization method for MySQL optimization. This article analyzes several optimization methods for RAND () in Mysql in detail, and finally draws a conclusion, if you want to directly order by rand () in

  If there is no srand () function and only RAND () function, the random numbers generated by each running program are the same. With the srand () function, the numbers generated each time are different. In C ++, you can use the rand () function to

[MySQL optimization case] series-RAND () optimization we all know that in MySQL, if order by rand () is used directly, the efficiency is very poor because it will be executed multiple times. In fact, this is also true if the equivalent query uses

Rand ()Returns a random value ranging from 0 to RAND_MAX. Before calling this function to generate a random number, you must use srand () to set the random number seed. If no random number seed is set, rand () will automatically set the random

As we all know, in MySQL, if direct order by RAND (), the efficiency is very poor, because it will be executed multiple times. In fact, if the equivalent query is also in RAND (), let's take a look at the different execution plans and execution time