This example creates random data from a predefined list of valid values:
```sql
insert into transactions(description, price, timestamp) values(
('{Bought cat,Bought dog,Bought house}'::text[])[ceil(random()*3)],
('{10,20}'::int[])[ceil(random()*2)],
NOW() - '1 day'::INTERVAL * ROUND(RANDOM() * 100)
)
```
This sets a column to a random UUID:
```sql
UPDATE customers SET name = uuid_in(md5(random()::text || clock_timestamp()::text)::cstring);
```