Incrementing ID on a SQL row that you cannot use the Identity property with.

This is most common when the identity is not the primary key, and is tracked independently for each Foreign Key Ref.


Field Type
OrderID Uniqueidentifier FK to the the order table.
LineNumber Int The column that we need each entry to unique per OrderId, but always start from 0.
Item Varchar(MAX)

A simple solution, (simplifying the table above to single column) would be:

Lets set up our test environment.

DECLARE @X int = null
DECLARE @T Table(row INT)

Run this once as is, then run this once with the next two lines commented out.

VALUES (0),(1),(2),(3),(4),(5),(6)

Here is the bulk of the actual work that you should learn from.

SET @X = 0
IF (
    (SELECT COUNT(1) FROM @T) > 0
    SELECT @X = MAX(row) + 1 FROM @T

And your proof

This entry was posted in Brian's Code Extreme, SQL, T-SQL and tagged , , . Bookmark the permalink.

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