The 
Optionally, you can insert an integer as a parameter.
Example:
derive type:single value: RAND() as:'random' 
Output: For each row, generate a random number between 0 and 1 in the new random
function.
Example with seed value:
derive type:single value: RAND(2) as:'random' 
Output: For each row, generate a random number between 0 and 1 in the new random
function. The generated random set of random values are consistent between job executions and are, in part, governed by the seed value 2
.
There are no arguments for this function.
derive type:single value: RAND([int_value]) 
Argument  Required?  Data Type  Description 

int_value  N  integer  Integer literal 
Optional Integer literal that is used to generate random numbers. Use of a seed value ensures consistency of output between job executions.
Required?  Data Type  Example Value 

No  Integer literal  14

In the following example, the random
column is generated by the RAND
function:
derive type:single value:RAND() as:'random' 
source  random 

A 

B 

C 

D 

The RAND
function is typically used to introduce randomness of some kind in your data. In the following example, it is used to perform sampling within your wider dataset.
Tip: Keep in mind that for larger datasets the application displays only a sample of them. This method of randomization is applied to the full dataset during job execution. 
Source:
You want to extract a random sample of 20% of your set of orders for further study:
OrderId  Qty  ProdId 

1001  30  Widgets 
1002  10  Big Widgets 
1003  5  Big Widgets 
1004  40  Widgets 
1005  80  Tiny Widgets 
1006  20  Widgets 
1007  100  Tiny Widgets 
Transform:
You can use the following transform to generate a random integer from one to 10:
derive type:single value:round(RAND() * 10) as:'random' 
You can now use the following transform to keep only the rows that contain random values that are in the top 20%, where the value is 9
or 10
:
keep row:(random > 8) 
Results:
NOTE: Since the results are randomized, your results might vary. 
OrderId  Qty  ProdId  random 

1005  80  Tiny Widgets  9 
1007  100  Tiny Widgets  10 