Answer by Samay for Add a column with a default value to an existing table in SQL Server

In SQL Server, you can use below template:

ALTER TABLE {tablename}
ADD 
    {columnname} {datatype} DEFAULT {default_value}

For example, to add a new column [Column1] of data type int with default value = 1 into an existing table [Table1] , you can use below query:

ALTER TABLE [Table1]
ADD 
    [Column1] INT DEFAULT 1