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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 column to be less than 3 characters. What is the expression I must use?
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You can define CHECK constraints at the column level, where the constraint applies only to a single column, and at the table level. You can also add CHECK constraints to a table using ADD CONSTRAINT .
The syntax for creating a check constraint in an ALTER TABLE statement in SQL Server (Transact-SQL) is: ALTER TABLE table_name ADD CONSTRAINT constraint_name CHECK (column_name condition); table_name.
Microsoft recommends no more than 253 foreign key constraints per column, though you are only limited by the number of objects in a database (2,147,483,647).
Discussion: Use the view table_constraints in the information_schema schema. The column table_name gives you the name of the table in which the constraint is defined, and the column constraint_name contains the name of the constraint.
use:
ALTER TABLE [dbo].[YOUR_TABLE]
ADD CONSTRAINT [MinLengthConstraint] CHECK (DATALENGTH([your_column]) > 2)
Reference:
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