How to autocomplete SQL field based on same row fields - sql

Question

QUESTION HAS BEEN UPDATED:Let's say I have two tables:Table1
ID_Ticket | Ticket_Quantity | Total_Price(Calculated field)
--------------------------------------------
2 | 5 | x
1 | 3 | y
Table2
ID_Ticket | Ticket_Price
------------------------
1 | 4.5
2 | 5
I want to prevent the user of the database to fill the field of Total_Price (via Edit Top 200 Rows or queries), instead I want it to be calculated as Ticket_Price * Ticket_Quantity and be inserted automatically on that row. In this case, x should be 25 and y should be 13.5 (the values should be insterted automatically once Ticket_Quantity and Ticket_Price are filled for that row)I wrote a function like this:
CREATE FUNCTION Multiply(#x DECIMAL(19,4), #y DECIMAL (19,4))
RETURNS DECIMAL(19,4)
AS
BEGIN
SELECT #x * Ticket_Price
FROM Table2
WHERE ID_Ticket = #y
ENDBut there is an error:Select statements included within a function cannot return data to a client Also when I want to add the calculated field based on the function:ALTER TABLE Purchases
ADD Total_Price AS Multiply(Table2.Ticket_Price,Ticket_Quantity); The query doesn't execute and gives me this error:
The multi-part identifier "Product.Prod_Price" could not be bound.
How should I call the values from Table2 and fix the Multiply function?

Answer 1

I found a solution, so I'll post it for future readers who have the same problem:
In the Object Explorer (left panel) go to this path:
Databases --> <your_database_name> --> programmability --> functions
Right-click on the Functions folder and select New --> Scalar-valued function
Paste the following function script (replace < variables > with those that correspond to your database):
CREATE FUNCTION dbo.Multiply(#id INT, #price DECIMAL(19,4))
--or (#x float, #y money) depending on the type of your columns you have
RETURNS DECIMAL(19,4)
--RETURNS <data_type_of_the_calculated_column_you_want>
AS
BEGIN
RETURN
(SELECT #price * Ticket_Price
--SELECT #<second_argument/column_name_of_Table1>*<column_name_of_Table2>
FROM Table2
--FROM <your_Table2_name>
WHERE ID_Ticket = #id)
--WHERE <unique/PrimaryKey_Column_to_identify_the_row_in_Table2>
-- = #<ForeignKey_Column_to_identify_the_row_in_Table2>
END
And execute it.
Now Create a new query (Ctrl+N) to add the calculated column in Table1, and copy-paste the following query:
ALTER TABLE Table1
--ALTER TABLE <your_Table1_name>
ADD Total_Price AS dbo.Multiply(ID_Ticket,Ticket_Quantity);
--ADD <name_of_the_calculated_row_you_like> AS
-- dbo.<Function_Name>(<id_column_name_of_Table2>,<column_name_from_Table1>)
Execute the query.
Now the calculated column should be the multiplication of the columns of Table1 and Table2