12123|12345678
42142|23442253
52315|32250205
....
....
...
....
....
around 50 million

Now I want to at random choose records and change the value of the second column

For example if I choose the second record at random. I will change the 2nd column to a random value:

12123|12345678
42142|53988989
52315|32250205
....
....
...
....
....

same operation 1 million times each time choosing a different record at random.