例子：

ALTER TABLE [Employees] ADD Seniority int not null default 0 GO

IF NOT EXISTS (
    SELECT * FROM INFORMATION_SCHEMA.COLUMNS
    WHERE TABLE_NAME ='TABLENAME' AND COLUMN_NAME = 'COLUMNNAME'
)
BEGIN
    ALTER TABLE TABLENAME ADD COLUMNNAME Nvarchar(MAX) Not Null default
END

例子：

ALTER TABLE tes 
ADD ssd  NUMBER   DEFAULT '0';

ALTER TABLE <table name> 
ADD <new column name> <data type> NOT NULL
GO
ALTER TABLE <table name> 
ADD CONSTRAINT <constraint name> DEFAULT <default value> FOR <new column name>
GO

--Adding Value with Default Value
ALTER TABLE TestTable
ADD ThirdCol INT NOT NULL DEFAULT(0)
GO

添加可为空的列时，WITH VALUES将确保将特定的DEFAULT值应用于现有行：

ALTER TABLE table
ADD column BIT     -- Demonstration with NULL-able column added
CONSTRAINT Constraint_name DEFAULT 0 WITH VALUES