How to Add Constarint in Table Create Command

CREATE TABLE ProductSales(SalesID INT,ProductID INT,SalesPerson VARCHAR(25)CONSTRAINT pk_productSales_sid PRIMARY KEY(SalesID),CONSTRAINT fk_productSales_pidFOREIGN KEY(ProductID)REFERENCES Products(ProductID) ON DELETE CASCADE
);


You can specify ON DELETE CASCADE also in Foreign Key Constraint
You Can also Create Foreign Key constraint Like this......


CREATE TABLE Orders
(
O_Id INT NOT NULL,
OrderNo INT NOT NULL,
P_Id INT,
PRIMARY KEY (O_Id),
CONSTRAINT fk_PerOrders FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)
)


You Can Also Add Constraint by Using Alter Command also 


ALTER TABLE ProductSalesADD CONSTRAINT fk_productSales_pid FOREIGN KEY(ProductID)REFERENCES Products(ProductID)

Window beforeunload Event

 Description :
                       This event fires before page leave .You can also ask confirmation on page leave.

In JQuery Use this syntax to bind Beforeunload Event



$(window).bind("beforeunload",function(event) {
    if(hasChanged) return "You have unsaved changes";
});




And if You want to Perform some action on page leave and not want confirmation Dialog Box

$(window).bind("beforeunload",function(event) {

    if(hasChanged) alert('Hello');

         null;

});