Unique integer numbers an populate columns

[Johan Nieuwoudt]

I created a table with an auto increment id and just 3 columns named testno1, testno2 and testno3.
How do I use a sql statement to update the table with testno1 containing 500 random integers between 1 and 1000.
Column testno2 containing 300 integers between 1 and 1000, not in testno1.
Column testno3 containing 200 random integers between 1 and 1000, not in testno1 and testno2.
The resulting table should then consist of unique random integers between 1 and 1000 and the integers values should not have duplicates in the 3 columns.
The columns with lesser rows can contain null values up to row 500.