how to do foreign key in sql code example

Example 1: alter table add column and foreign key mysql

ALTER TABLE database.table
  ADD COLUMN columnname INT DEFAULT(1),
  ADD FOREIGN KEY fk_name(fk_column) REFERENCES reftable(refcolumn) ON DELETE CASCADE;

Example 2: foreign key mssql

CREATE TABLE Sales.TempSalesReason 
   (
      TempID int NOT NULL, Name nvarchar(50)
      , CONSTRAINT PK_TempSales PRIMARY KEY NONCLUSTERED (TempID)
      , CONSTRAINT FK_TempSales_SalesReason FOREIGN KEY (TempID)
        REFERENCES Sales.SalesReason (SalesReasonID)
        ON DELETE CASCADE
        ON UPDATE CASCADE
   )
;