Question

I have the following table:

tbl_ProductCatg

Id    IDENTITY
Code
Description
a few more.

Id field is auto-incremented and I have to insert this field value in Code field.

i.e. if Id generated is 1 then in Code field the value should be inserted like 0001(formatted for having length of four),if id is 77 Code should be 0077.

For this, I made the query like:

insert into tbl_ProductCatg(Code,Description)
values(RIGHT('000'+ltrim(Str(SCOPE_IDENTITY()+1,4)),4),'testing')

This query runs well in sql server query analyzer but if I write this in C# then it insets Null in Code even Id field is updated well.

Thanks

Answer 1

You may want to look at Computed Columns (Definition)

From what is sounds like you are trying to do, this would work well for you.

CREATE TABLE tbl_ProductCatg
(
   ID INT IDENTITY(1, 1)
   , Code AS RIGHT('000' + CAST(ID AS VARCHAR(4)), 4)
   , Description NVARCHAR(128)
)

or

ALTER TABLE tbl_ProductCatg
ADD Code AS RIGHT('000' + CAST(id AS VARCHAR(4)), 4)

You can also make the column be PERSISTED so it is not calculated every time it is referenced.

Marking a column as PERSISTED Specifies that the Database Engine will physically store the computed values in the table, and update the values when any other columns on which the computed column depends are updated.