SQL Trigger that should update other table - sql

Question

I am trying to make a trigger that will update a table only if something is inserted in an other table
CREATE TABLE Purchases
(
PurchaseID INT IDENTITY NOT NULL PRIMARY KEY,
DateBought SMALLDATETIME,
Price MONEY CHECK (Price>0),
RealEstateID INT UNIQUE NOT NULL,
DealMadeByEmployeeID INT NOT NULL
);
INSERT INTO Purchases(DateBought, Price, RealEstateID, DealMadeByEmployeeID)
VALUES ('20161015 15:10:03','120000',3, 3); --Апартамент 170 квадратни метра
INSERT INTO Purchases(DateBought, Price, RealEstateID, DealMadeByEmployeeID)
VALUES ('20161219 13:13:30','200000',4, 3); --Къща 500 квадратни метра
INSERT INTO Purchases (Price,RealEstateID,DealMadeByEmployeeID)
VALUES ('130000',6,3); --непродаден апартамент
CREATE TABLE EmployeesSalary
(
EmployeeID INT NOT NULL PRIMARY KEY,
CurrentSalary MONEY DEFAULT 0,-- на процент
MonthlySalesMade INT DEFAULT 0,
MonthlyRentsMade INT DEFAULT 0
);
INSERT INTO EmployeesSalary (EmployeeID, CurrentSalary)
VALUES (1, '400');
INSERT INTO EmployeesSalary (EmployeeID, CurrentSalary)
VALUES (2, '400');
INSERT INTO EmployeesSalary (EmployeeID, CurrentSalary)
VALUES (3, '400');
CREATE TRIGGER tr_EmployeesSalaryPurchasesUpdate --при INSERT в Purchases таблицата
ON Purchases
AFTER INSERT
AS
BEGIN
UPDATE EmployeesSalary
SET EmployeesSalary.MonthlySalesMade=EmployeesSalary.MonthlySalesMade+1
WHERE EmployeesSalary.EmployeeID IN (SELECT inserted.DealMadeByEmployeeID FROM inserted)
END
but based on the IDs.
My code doesn't get any errors but the trigger doesn't seem to work. What is my mistake?
https://postimg.org/image/rot0xcriv/

Answer 1

You should use an INNER JOIN there:
CREATE TRIGGER tr_EmployeesSalaryPurchasesUpdate --при INSERT в Purchases таблицата
ON Purchases
AFTER INSERT
AS
BEGIN
UPDATE ES
SET ES.MonthlySalesMade = ES.MonthlySalesMade+1
FROM EmployeesSalary ES
INNER JOIN INSERTED I
ON ES.EmployeeID = I.DealMadeByEmployeeID;
END

Answer 2

It won't work if there are multiple updates unless NOCOUNT is SET to ON:
CREATE TRIGGER tr_EmployeesSalaryPurchasesUpdate
ON Purchases
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON -- new line of code
UPDATE EmployeesSalary
SET EmployeesSalary.MonthlySalesMade=EmployeesSalary.MonthlySalesMade+1
WHERE EmployeesSalary.EmployeeID IN (SELECT inserted.DealMadeByEmployeeID FROM inserted)
END

Answer 3

You can also use the EXISTS operator.
Also beaware of the possible NULLS in MonthlySalesMade column, +1 update will not work if there is a null values in that column.
CREATE TRIGGER tr_EmployeesSalaryPurchasesUpdate
ON Purchases
AFTER INSERT
AS
BEGIN
UPDATE EmployeesSalary
SET MonthlySalesMade = ISNULL(MonthlySalesMade, 0)+1
WHERE EXISTS (SELECT 1
FROM inserted
WHERE EmployeesSalary.EmployeeID = inserted.DealMadeByEmployeeID )
END