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Displaying posts with tag: rand() (reset)
Quick Password generation with MySQL

Here is a quick and simple way to generate a password your application using MySQL.
This query will create a upper and lower case randomly generated password in length and values.


SELECT CONCAT(UCASE(SUBSTRING(  SUBSTRING(MD5(RAND()), FLOOR( 1 + (RAND() * 5)) , FLOOR( 8 + (RAND() * 15 )) )   , FLOOR( 1 + (RAND() * 4 )) , FLOOR( 4 + (RAND() * 12 )) )),
SUBSTRING('!@#$%^&*', FLOOR( 1 + (RAND() * 4))  , FLOOR( 1 + (RAND() * 8))  ),
SUBSTRING(  SUBSTRING(MD5(RAND()), FLOOR( 1 + (RAND() * 5)) , FLOOR( 8 + (RAND() * 15 )) ) , 5)) as password \G


This query will take a random value for the 1st part of the dynamic password and upper case it when applicable then the second half it adds some symbols then the remaining is in lower case because MD5 does that automatically. You of course can adjust whatever symbols you would prefer.

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MySQL random integers

This is not a new feature by any means but it is a question I have happen to see pop up every now and then. So a quick example is following.

To generate a random integer within MySQL you can use the Floor and Rand functions. The MySQL manual documents this here: http://dev.mysql.com/doc/refman/5.5/en/mathematical-functions.html#function_rand

"To obtain a random integer R in the range i <= R < j, use the expression FLOOR(i + RAND() * (j – i))"

So to give an example:

> SET @I = 3; # lower range
> SET @J = 43 - @I; # max range minus lower range

> SELECT FLOOR( @I + (RAND() * @J )) as lottery_numbers\G

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How to select random rows in MySQL

The easiest way to generate random rows in MySQL is to use the ORDER BY RAND() clause. SELECT col1 FROM tbl ORDER BY RAND() LIMIT 10; This can work fine for small tables. However, for big table, it will have a serious performance problem as in order to generate the list of random rows, MySQL […]

MySQL random data selection

Some days ago I was working in a vocabulary game and dictionary. The dictionary contains 1,10,000 words and meanings. I developed a vocabulary game where I had to randomly choose 10 words out of 1,10,000 dataset. Here I’m describing the possible solutions for this problem and which solution I used.

Data table

Table name is dictionary and it has id, word and meaning fields. id contains auto incremented id and it is unbroken sequence 1,2,3…..n.

id word meaning
1 aback Having the wind against the forward side of the sails
2 abandon Forsake, leave behind
….. …. …
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Showing entries 1 to 4