SQL Server Error: Arithmetic overflow error converting int to data type numeric

smile says:

CAST(Quantity AS DECIMAL(2,0))

The error is due to Decimal declaration.

Your Qty field is having length of 3 i.e. 100. But you are trying to CAST with 2.

Change the size of the DECIMAL.

Check the below query.

SQL

DECLARE @Test AS TABLE(ID INT,Size INT,Qty INT)
INSERT INTO @Test VALUES(1,40,100)
INSERT INTO @Test VALUES(2,45,100)
INSERT INTO @Test VALUES(3,50,100)
SELECT ID,Size,Qty,
CAST(CAST(Qty AS DECIMAL(3,0))/CAST(Size AS DECIMAL(4,0)) AS DECIMAL(10,2)) Total
FROM @Test

Output

ID  Size  Qty    Total

1    40    100    2.50

2    45    100    2.22

3    50    100    2.00