你可以使用 ALTER TABLE 命令来添加默认约束。以下是实现这一操作的 SQL 代码: -- 为 JoiningDate 列添加默认约束ALTERTABLEEmployeesADDCONSTRAINTDF_JoiningDateDEFAULTGETDATE()FORJoiningDate;-- 这段代码将为 JoiningDate 列添加一个名为 DF_JoiningDate 的默认约束,-- 使用 GETDATE() 函数为该列设置当前日期...
T-SQL GETDATE() ? ADD and SUBTRACT depending on the condition is CASE STATEMENT ADD COLUMN to variable table? Add prefix in data column Add Time in SQL HH:MM:SS to another HH:MM:SS Adding a column to a large (100 million rows) table with default constraint adding a extra column i...
1、添加主键约束: 格式:alter table 表名 add constraint 约束名称 primary key(列名) 例子:alter table ss add constraint pp primary key(sid) 2、添加外键约束: 格式:alter table 表名 add constraint 约束名称 foreign key(列名) references 被引用表的名称(列名) 例子:alter table ss add constraint pp fo...
the default value will be added to the table. The following script makes use of SQL Server ALTER TABLE ADD Column (Status in our case) statement to add a column named Status with default constraint.
How to: To SQL add a column with a default value is a simple operation in SQL. Let us set up a ‘student’ table as below:
SQL: add constraint 方法添加约束 alter table 表名 add constraint 约束名称 约束类型(列名) 1、添加主键约束: 格式:alter table 表名 add constraint 约束名称 primary key(列名) 例子:alter table ss add constraint pp primary key(sid) 2、添加外键约束: ...
Adding a brand_id smallint column with a default value: altertableproductsaddbrand_idsmallintdefault1; Adding a string (varchar) column with a not null constraint: --note:this is possible only if the table contains no data!!altertableproductsadddescriptionvarchar(100)notnull; ...
alter table emp add constraint qwe unique(ename); 4.默认约束:意思很简单就是让此列的数据默认为一定的数据 格式: alter table 表名称 add constraint 约束名称 约束类型 默认值) for 列名 例子: alter table emp add constraint jfsddefault 10000 for gongzi; ...
1.1 Enhanced ADD COLUMN Functionality Default valuesof columns are maintained in the data dictionary for columns specifiedas NOT NULL. --当列指定为not null,那么该列对应的默认值在数据字典中进行维护。 Adding newcolumns with DEFAULT values and NOT NULL constraint nolonger requires the default value to...
Example 2: Adding a Column with Constraints We can also add a new column with various constraints as shown in the following example query: ALTER TABLE employees ADD COLUMN salary DECIMAL(10,2)NOT NULL; In this example, we add a new column called “salary” with a NOT NULL constraint to ...