# Tim Van Wassenhove

Passionate geek, interested in Technology. Proud father of two

Earlier this week some colleague had been assigned a maintenance task and asked me how I would solve it. Every customer is permitted to have an amount of publications. All excess publications should be removed from the system (only the n most recent ones are permitted to remain on the system).

Here is an example of the Customer table:

``````CREATE TABLE [dbo].[Customer](
[CustomerId] [int] IDENTITY(1,1) NOT NULL,
[CustomerName] [nvarchar](50) NOT NULL,
[PermittedPublications] [int] NOT NULL
);

INSERT INTO [dbo].[Customer]
([CustomerName], [PermittedPublications])
VALUES
('timvw', 2),
('mike', 3);
``````

An example of the customer publications table:

``````CREATE TABLE [dbo].[Publication](
[PublicationId] [int] IDENTITY(1,1) NOT NULL,
[CustomerId] [int] NOT NULL,
[PublicationName] [nvarchar](50) NOT NULL,
[PublicationTime] [datetime2] NOT NULL
);

INSERT INTO [dbo].[Publication]
([CustomerId], [PublicationName],[PublicationTime])
VALUES
((SELECT [CustomerId] FROM [dbo].[Customer] WHERE [CustomerName] = 'timvw'), 'tim pub1', SYSUTCDATETIME()),
((SELECT [CustomerId] FROM [dbo].[Customer] WHERE [CustomerName] = 'timvw'), 'tim pub2', SYSUTCDATETIME()),
((SELECT [CustomerId] FROM [dbo].[Customer] WHERE [CustomerName] = 'timvw'), 'tim pub', SYSUTCDATETIME()),
((SELECT [CustomerId] FROM [dbo].[Customer] WHERE [CustomerName] = 'timvw'), 'tim pub4', SYSUTCDATETIME()),
((SELECT [CustomerId] FROM [dbo].[Customer] WHERE [CustomerName] = 'mike'), 'mike pub1', SYSUTCDATETIME()),
((SELECT [CustomerId] FROM [dbo].[Customer] WHERE [CustomerName] = 'mike'), 'mike pub2', SYSUTCDATETIME());
``````

My colleague was keen on using some cursor logic, but I demonstrated him how a set-based alternative:

``````WITH [RankedPublication] AS (
SELECT [CustomerId]
,[PublicationId]
,[PublicationName]
,[PublicationTime]
,ROW_NUMBER() OVER(PARTITION BY [CustomerId] ORDER BY [PublicationTime]) AS [PublicationRank]
FROM [dbo].[Publication]
), [ExcessPublication] AS (
SELECT [PublicationId]
FROM [RankedPublication]
INNER JOIN [dbo].[Customer] ON [Customer].[CustomerId] = [RankedPublication].[CustomerId]
WHERE [PublicationRank] > [Customer].[PermittedPublications]
)
DELETE FROM [dbo].[Publication]
WHERE [PublicationId] IN (SELECT [PublicationId] FROM [ExcessPublication]);
``````