SQL Server 2022

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE MyTable (
  ID INTEGER,
  UserID INTEGER,
  RecordedTransaction VARCHAR(8),
  RecordedAmount FLOAT
);

INSERT INTO MyTable
  (ID, UserID, RecordedTransaction, RecordedAmount)
VALUES
  ('1', '12345678', 'Purchase', '0.10'),
  ('2', '12345678', 'Deposit', '100.00'),
  ('3', '12345678', 'Purchase', '100.00'),
  ('4', '12345678', 'Deposit', '30.00'),
  ('5', '12345678', 'Purchase', '30.00'),
  ('6', '12345678', 'Deposit', '25.00'),
  ('7', '12345678', 'Purchase', '0.80');
7 rows affected

 UPDATE a 
 SET a.RecordedAmount = case when RecordedTransaction = 'Deposit' THEN FLOOR(RAND() * (20- 10 + 1)) + 10 
 ELSE ROUND(
 (CAST(RAND(CHECKSUM(NEWID())) * 
 (CASE WHEN  RecordedAmount < 0.99 THEN RecordedAmount ELSE 0.99 END) AS FLOAT) + 0.01 )
 ,2,0) end
 FROM dbo.MyTable a
7 rows affected

SELECT * fROM MyTable


ID
UserID
RecordedTransaction
RecordedAmount


1
12345678
Purchase
0.06

2
12345678
Deposit
20

3
12345678
Purchase
0.22

4
12345678
Deposit
20

5
12345678
Purchase
0.46

6
12345678
Deposit
20

7
12345678
Purchase
0.64

ID	UserID	RecordedTransaction	RecordedAmount
1	12345678	Purchase	0.06
2	12345678	Deposit	20
3	12345678	Purchase	0.22
4	12345678	Deposit	20
5	12345678	Purchase	0.46
6	12345678	Deposit	20
7	12345678	Purchase	0.64