Randy Minder Randy Minder - 1 month ago 4
SQL Question

Command for adding a default constraint

There appears to be at least two ways to add a default constraint using straight T-SQL. Am I correct that the only difference between the two below is that the second method specifically creates a name for the constraint, and the first method has one generated by SQL Server?

ALTER TABLE [Common].[PropertySetting] ADD DEFAULT ((1)) FOR [Active];
ALTER TABLE [Common].[PropertySetting] ADD CONSTRAINT [DF_PropertySetting_Active) DEFAULT ((1)) FOR [Active];

gbn gbn
Answer

Pretty much, yes for an ALTER TABLE

You can add a columnn with default in one step for CREATE or ALTER too.

ALTER TABLE foo ADD bar varchar(100) CONSTRAINT DF_Foo_Bar DEFAULT ('bicycle')
ALTER TABLE foo ADD bar varchar(100) DEFAULT ('bicycle')

As you noted, the system generates a name if one is not supplied. CONSTRAINT constraint_name is optional says MSDN. The same applies to any column or table CONSTRAINT

Edit If the column was already created, and you only want to add the constraint use:

ALTER TABLE TableName ADD CONSTRAINT DF_Foo_Bar DEFAULT 'bicycle' FOR FieldName;