Generating random student data - sql

Question

I'm trying to create a process that populates a student table. I want to be able to create a different combination of a student's first/last name and dob every time I run the query.
The code below appears to work fine as it generates 5 names. My first question is can this be modified to generate N NUMBER of rows sat for example 20. I tried using CONNECT by level <=20 but that gives me a syntax error.
Secondly, know the random_date function works
Select random_date(DATE '2001-01-01', DATE '2001-12-31') from dual
17-NOV-2001 08:31:16
But I can't seem to incorporate into my SQL.
Any help would be greatly appreciated. Thanks in advance for your expertise and time
ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'DD-MON-YYYY HH24:MI:SS.FF';
ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';
CREATE OR REPLACE FUNCTION random_date(
p_from IN DATE,
p_to IN DATE
) RETURN DATE
IS
BEGIN
RETURN p_from + DBMS_RANDOM.VALUE() * (p_to - p_from + 1 );
END random_date;
/
CREATE TABLE students (
student_id number(*,0),
first_name VARCHAR(25) NOT NULL,
last_name VARCHAR(25) NOT NULL,
dob DATE,
constraint teacher_pk primary key (student_id));
WITH raw_names (first_name, last_name) AS
(
SELECT 'Faith', 'Andrews' FROM dual UNION ALL
SELECT 'Tom', 'Thornton' FROM dual UNION ALL
SELECT 'Anna', 'Smith' FROM dual UNION ALL
SELECT 'Lisa', 'Jones' FROM dual UNION ALL
SELECT 'Andy', 'Beirs' FROM dual
)
, numbered_names AS
(
SELECT first_name, last_name
, ROW_NUMBER () OVER (ORDER BY dbms_random.value (0, 1)) AS first_num
, ROW_NUMBER () OVER (ORDER BY dbms_random.value (0, 2)) AS last_num
FROM raw_names
)
SELECT fn.first_num AS student_id
, fn.first_name
, ln.last_name
FROM numbered_names fn
JOIN numbered_names ln ON ln.last_num = fn.first_num
ORDER BY student_id
;

Answer 1

I can't debug your code as you didn't post it (the one that raised a syntax error and doesn't accept the function).
Anyway, here's what you might do:
line #14 - function call
lines #15 - 19 show how to create desired number of rows (must be multiple of number of rows in raw_names)
SQL> WITH raw_names (first_name, last_name) AS
2 (
3 SELECT 'Faith', 'Andrews' FROM dual UNION ALL
4 SELECT 'Tom', 'Thornton' FROM dual UNION ALL
5 SELECT 'Anna', 'Smith' FROM dual UNION ALL
6 SELECT 'Lisa', 'Jones' FROM dual UNION ALL
7 SELECT 'Andy', 'Beirs' FROM dual
8 )
9 , numbered_names AS
10 (
11 SELECT first_name, last_name
12 , ROW_NUMBER () OVER (ORDER BY dbms_random.value (0, 1)) AS first_num
13 , ROW_NUMBER () OVER (ORDER BY dbms_random.value (0, 2)) AS last_num
14 , random_date (date '2001-01-01', date '2001-12-31') datum
15 FROM raw_names cross join
16 table(cast(multiset(select level from dual
17 connect by level <= (select &n / count(*) from raw_names))
18 as sys.odcinumberlist))
19 )
20 SELECT fn.first_num AS student_id
21 , fn.first_name
22 , ln.last_name
23 , ln.datum
24 FROM numbered_names fn
25 JOIN numbered_names ln ON ln.last_num = fn.first_num
26 ORDER BY student_id
27 ;
Enter value for n: 20
Result:
STUDENT_ID FIRST LAST_NAM DATUM
---------- ----- -------- --------------------
1 Tom Andrews 12-NOV-2001 14:42:05
2 Faith Jones 06-MAR-2001 05:14:07
3 Tom Thornton 04-SEP-2001 16:28:25
4 Faith Beirs 29-MAR-2001 06:11:35
5 Andy Thornton 18-MAY-2001 17:32:07
6 Andy Jones 19-JAN-2001 19:39:15
7 Anna Jones 17-JAN-2001 02:51:39
8 Andy Andrews 31-DEC-2001 15:36:44
9 Faith Beirs 22-JUN-2001 05:34:22
10 Lisa Thornton 29-JUL-2001 07:00:15
11 Lisa Smith 31-JAN-2001 04:17:04
12 Anna Andrews 07-FEB-2001 09:02:21
13 Lisa Thornton 31-DEC-2001 20:18:06
14 Lisa Smith 24-SEP-2001 04:10:21
15 Tom Andrews 30-JUN-2001 12:01:04
16 Faith Jones 16-AUG-2001 19:56:54
17 Anna Beirs 23-NOV-2001 11:01:03
18 Anna Beirs 23-NOV-2001 08:33:39
19 Andy Smith 24-SEP-2001 21:27:00
20 Tom Smith 24-SEP-2001 22:07:39
20 rows selected.
SQL>