How to Allow Only Alphabets in Column? – Interview Question of the Week #136

Question: How to Allow Only Alphabets in Column?

Answer: This was a real world scenario and I have mixed feeling about this kind of question being asked in interviews. However, let us accept this question as it is and let us see how to solve this problem.

 

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How to Allow Only Alphabets in Column? - Interview Question of the Week #136 alphabets-800x450

To allow only alphabets in a column the user can create a check constraint over column to allow insertion of alphabets in the column. Here is a sample script where I demonstrate how users can create constraint over column first so it only allows alphabets.

Let us see the script how we can do so.

USE tempdb
GO
-- Create Test table
CREATE TABLE TestTable
(ID INT, FirstCol VARCHAR(100),
CONSTRAINT FirstCol CHECK (FirstCol NOT LIKE '%[^A-Z]%'))
GO
-- This will be successful
INSERT INTO TestTable (ID, FirstCol)
VALUES (1, 'SQLAuthority')
GO
-- This will throw an error
INSERT INTO TestTable (ID, FirstCol)
VALUES (1, 'SQLAuthority 1')
GO
-- Clean up
DROP TABLE TestTable
GO

Well, that’s it. A good constraint solves the problem about allowing only alphabets in the column. If you have any other solution, please post it over here. I have previously seen many samples, but none of the example really worked well.

So if you have a good solution, I request you to post in the comments area and I will post it with due credit.

Reference: Pinal Dave (https://blog.sqlauthority.com)

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