What's the difference between a column with a default and a column with a default constraint?

A default value of a column can be added like this

ALTER TABLE [MyTable] ADD DEFAULT ((0)) FOR [MyColumn]

or like this

ALTER TABLE [MyTable] ADD CONSTRAINT [DF_MyTable_MyColumn]  DEFAULT ((0)) FOR开发者_如何转开发 [MyColumn]

What is the difference between the two?

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The constraint in the first example will be assigned a name by SQL Server.

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SQL Server peculiarly classifies defaults as "constraints". The syntax using the CONSTRAINT keyword allows you to specify a name for the default, which is good practice.