Firebird Interview Question:

How to select a random record from a table?

Submitted by: Administrator

There is no such feature in Firebird, but you can use some tricks. The following example requires that you have a unique integer column (primary key is usually used):

SELECT ...field_list...
FROM table t1
WHERE conditions
ORDER BY (t1.int_col + seed)*4294967291-((t1.int_col + seed)*4294967291/49157)*49157;

If you just need one random record, limit the result set using FIRST or ROWS clause. This query will give consistent records for the same seed. If you wish to be completely random, you need to change the seed. You could use the value of int_col from previous run, or simply fetch a new value from a generator (just make sure the same value for seed is used in both places in expression).
Submitted by: Administrator