Listing 1: DBMS_RANDOM normal function
The DBMS_RANDOM NORMAL function returns numbers with a normal distribution.
SQL> create table t
2 as
3 select dbms_random.normal
4 from all_objects
5 /
Table created.
SQL> select count(*),
2 sum( decode( ceil(abs(normal)), 1, 1, 0 ) )/count(*) "+/- 1 stddev",
3 sum( decode( ceil(abs(normal)), 1, 1, 2, 1, 0 ) )/count(*) "+/- 2 stddev",
4 sum( decode( ceil(abs(normal)), 1, 1, 2, 1, 3, 1, 0 ) )/count(*) "+/- 3 stddev",
5 stddev(normal)
6 from t
7 /
COUNT(*) +/- 1 stddev +/- 2 stddev +/- 3 stddev STDDEV(NORMAL)
------- ------------ ------------ ------------ -------------
21958 .679433464 .954458512 .997495218 1.00407451
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