Calculated Date filed from another Date field that is Randomised - sql

Question

I have to create some random data and so far with the help of this forum I have done 80% of it but I am now stuck (again)
What I need is this I have a column called Requested Date, this date should randomised but be between 1 and 10 days later than the Order Date. Can this be done?
DECLARE #OrderNumber varchar (30)
DECLARE #OrderDate int
DECLARE #OrderLineNumber varchar(50)
DECLARE #CustomerSkey int
DECLARE #ProductSkey int
DECLARE #OrderMethodSkey int
DECLARE #Quantity int
DECLARE #Cost Decimal(18,3)
DECLARE #RequestedDate int
SET #OrderNumber = 1
SET #OrderDate = 0
SET #OrderLineNumber = 1
SET #CustomerSkey = 1
SET #ProductSkey = 1
SET #OrderMethodSkey = 1
SET #Quantity = 1
SET #Cost = 1
SET #RequestedDate = 0
WHILE #OrderNumber <= 100
WHILE #OrderDate <= 100
WHILE #OrderLineNumber <= 100
WHILE #CustomerSkey <= 100
WHILE #ProductSkey <= 100
WHILE #OrderMethodSkey <= 100
WHILE #Quantity <= 100
WHILE #Cost <= 100
WHILE #RequestedDate <= 100
BEGIN
INSERT INTO Orders
(OrderNumber
, OrderDate
, OrderLineNumber
, CustomerSkey
, ProductSkey
, OrderMethodSkey
, OrderTime
, Quantity
, Cost
, RequestedDate)
SELECT
'ORD' + Right ('000000' + CAST (#OrderNumber AS varchar (30)), 6)
,DATEADD (day, CAST (RAND () * 1500 as int), '2008-1-1')
,(Right ('0' + CAST (#OrderLineNumber AS varchar (30)), 6))
,(99 * RAND()) + 1
,(99 * RAND()) + 1
,(2 * RAND()) + 1
,DATEADD(ms, cast(86400000 * RAND() as int), convert(time, '00:00'))
,(190 * RAND()) + 10
,(40 * RAND()) + 10
,DATEADD (day, CAST (RAND () * 10 as int), #RequestedDate)
SET #OrderNumber = #OrderNumber + 1
SET #OrderDate = #OrderDate + 1
SET #OrderLineNumber = #OrderLineNumber + 1
SET #CustomerSkey = #CustomerSkey + 1
SET #ProductSkey = #ProductSkey + 1
SET #OrderMethodSkey = #OrderMethodSkey + 1
SET #Quantity = #Quantity + 1
SET #Cost = #Cost + 1
SET #RequestedDate = #RequestedDate + 1
END

Answer 1

In PostgreSQL you can do:
with t as (select '2013-01-01'::date as order_date)
select
order_date,
(order_date + round(.5 + 10*random()) * interval '1 day')::date as requested_date,
(order_date + round(.5 + 10*random()) * interval '1 day')::date - order_date as difference from t
0) random() function returns random number between 0 and 1
1) round(.5 + 10*random() will give you number between 1 and 10
2) random number is added to date as an interval in days
3) result is casted to date (because step 2 will return timestamp)
To prove that round(.5 + 10*random() gets random number between 1 and 10:
with t as (select round(.5 + 10*random()) rnd from generate_series(1,1000000,1))
select rnd, count(*) cnt from t group by rnd order by rnd
rnd cnt
1 100249
2 100817
3 99550
4 99813
5 100065
6 99468
7 100089
8 99652
9 99889
10 100408

Answer 2

you can calculate the value of order_date before the insert statement
add a new variable with the other declares
declare #od datetime
inside the while loops but before the insert statement set up the order date
select #od = DATEADD (day, CAST (RAND () * 1500 as int), '2008-1-1')
use this variable in the insert statement so
,DATEADD (day, CAST (RAND () * 1500 as int), '2008-1-1')
becomes
,#od
and use this value to calculate the request date, so
becomes
,DATEADD (day, CAST (RAND () * 10 as int), #RequestedDate)
and
,DATEADD (day, CAST (RAND () * 10 as int), #od)
sql fiddle