How can I create a CHECK constraint on a VARCHAR column in SQL Server specifying a minimum data length?

I have a VARCHAR(30) column in a Microsoft SQL Server database. I'd like to add a CHECK constraint that does not allow a value in the 开发者_开发知识库column to be less than 3 characters. What is the expression I must use?

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use:

ALTER TABLE [dbo].[YOUR_TABLE]
ADD CONSTRAINT [MinLengthConstraint] CHECK (DATALENGTH([your_column]) > 2)

Reference:

• DATALENGTH vs LEN
• SQL SERVER – 2005 Constraint on VARCHAR(MAX) Field To Limit It Certain Length