Fill up column with random values from different table - sql

Question

I have 2 tables. Table Table_View has 5 columns and 200 rows
and Table_Random has 3 columns with 10 rows
I need to poulate column Table_View.A_random with values from
Table_Random.FixValues. If the query reaches the end of row in Table_Random i.e row 10, it should start again with
values from the top row i.e row 1. until it fills up the 200 rows.
Given that all tables has primary keys.
Any Ideas?
Thanks in advance

Answer 1

This will work for any count of rows in destination and source tables.
The idea is to calculate count of rows in random table and then assign number rn % #c to each row in destination table. And then update based on join:
DECLARE #count INT = 21
DECLARE #i INT = 1
DECLARE #c INT = 0
DECLARE #t TABLE ( ID INT, Random INT )
DECLARE #r TABLE ( ID INT, Random INT )
INSERT INTO #r
VALUES ( 1, 10 ),
( 3, 20 ),
( 4, 30 ),
( 6, 40 ),
( 8, 50 ),
( 11, 60 ),
( 14, 70 ),
( 17, 80 ),
( 19, 90 ),
( 21, 100 )
WHILE #i <= #count
BEGIN
INSERT INTO #t
VALUES ( #i, NULL )
SET #i = #i + 1
END;
SELECT #c = COUNT(*)
FROM #r;
WITH ctet1
AS ( SELECT * , ROW_NUMBER() OVER ( ORDER BY ID ) AS rn
FROM #t
),
ctet2
AS ( SELECT * ,
CASE WHEN rn % #c = 0 THEN #c
ELSE rn % #c
END AS rnn
FROM ctet1
),
cter
AS ( SELECT * , ROW_NUMBER() OVER ( ORDER BY ID ) AS rn
FROM #r
)
UPDATE ct
SET Random = cr.Random
FROM ctet2 ct
JOIN cter cr ON cr.rn = ct.rnn
SELECT * FROM #t
Output:
ID Random
1 10
2 20
3 30
4 40
5 50
6 60
7 70
8 80
9 90
10 100
11 10
12 20
13 30
14 40
15 50
16 60
17 70
18 80
19 90
20 100
21 10
If you didn't want cycle update then no need for views, functions and needless stuff. Just update:
UPDATE #t SET Random = (SELECT TOP 1 Random FROM #r ORDER BY NEWID())

Answer 2

yes you can make this out.
First of all you need to create and view which'll return a single value from Random Table(Table_Random) for every call.
Create View vMyRand as
Select top 1 val from myRand order by NewID();
then create a function to return value from created view.
CREATE FUNCTION GetMyRand ()
RETURNS varchar(5)
--WITH EXECUTE AS CALLER
AS
BEGIN
Declare #RetValue varchar(5)
--#configVar =
Select #RetValue = val from vmyRand
RETURN(#retValue)
END;
Fiddle Demo Here
Full Code:
create table tab_1
(
id bigint identity(1,1),
name varchar(50),
email varchar(50)
)
insert into tab_1(name,email) values
('a','a#mail.com'), ('b','c#mail.com'),
('a1','a1#mail.com'), ('a2','a2#mail.com'),
('a3','a3#mail.com'), ('a4','a4#mail.com'),
('b1','b1#mail.com'),('b2','b2#mail.com')
create table myRand(val varchar(50))
insert into myRand values('Q1654'),('F2597'),
('Y9405'),('B6735'),('D8732'),('C4893'),('I9732'),
('L1060'),('H6720');
Create View vMyRand as
Select top 1 val from myRand order by NewID();
CREATE FUNCTION GetMyRand ()
RETURNS varchar(5)
--WITH EXECUTE AS CALLER
AS
BEGIN
Declare #RetValue varchar(5)
--#configVar =
Select #RetValue = val from vmyRand
RETURN(#retValue)
END;
Update Code:
update tab_1 set name=(select dbo.getMyRand())
Hope This'll Help You.
Thanks. :)