MySQL:
SELECT column FROM table ORDER BY RAND() LIMIT 1
注意这个语句，要在数据量小的情况下用（500条下），数量大的，请先计算出条数，然后生成随机数，再用SQL算出。

SQL Server:
SELECT TOP 1 column FROM table ORDER BY NEWID()

Oracle:
SELECT column FROM( SELECT column FROM table ORDER BY dbms_random.value )WHERE rownum = 1

PostgreSQL:
SELECT column FROM table ORDER BY RANDOM() LIMIT 1

IBM DB2:
SELECT column, RAND() as IDX FROM table ORDER BY IDX FETCH FIRST 1 ROWS ONLY