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I'm having problems setting a computed column as not null.
What I want to achieve is C001,C002..., etc. and at the same time set it as not null.
I have read on a forum that this can be achieved by using the default value 0 for NULL values.
E.g., ISNULL(Price + Taxes, 0)
I have tried to apply to this formula:
('C'+right('000'+CONVERT([varchar](3),[ID],(0)),(3)))
But it didn't seem to work. Can anyone tell me what am I missing?
ALTER CreditCard accountNo AS ISNULL('C'+right('000'+CONVERT([varchar](3),[idCreditCard],(0)),(3)),0)
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By default, a column can hold NULL values. The NOT NULL constraint enforces a column to NOT accept NULL values. This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to this field.
If you place a NOT NULL constraint on a column (and no default value is specified), you must enter a value into this column when you insert a row or update that column in a row. If you do not enter a value, the database server returns an error, because no default value exists.
Unique fields in SQL Server are created using unique constraints or unique indexes, furthermore, each unique constraint uses a unique index. Regardless of using unique constraint or unique index, the field can accept null values, however the uniqueness will result in only accepting a single row with null value.
I've finally found the solution to my problem!
The correct query should be:
ALTER TABLE CreditCard ADD accountNo AS ISNULL('C'+right('000'+CONVERT([varchar](3),[idCreditCard],(0)),(3)),0)
Thanks for the help guys!
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