CodeSOD: One Case

I feel like we've gotten a few SQL case statement abuses recently, but a properly bad one continues to tickle me. Ken C sends us one that, well:

SELECT CASE h.DOCUMENTTYPE WHEN 2 THEN 3 WHEN 3 THEN 4 WHEN 4 THEN 5 WHEN 5 THEN 6 WHEN 6 THEN 7 WHEN 7 THEN 8 ELSE h.DOCUMENTTYPE END AS DocumentType, h.DOCNMBR AS DocNmbr, h.FULLPOLICY AS FullPolicy, h.BATCHID AS BatchId, h.OrigBatchId, h.UPDATEDDATE AS UpdatedDate, h.CUSTOMERNO AS CustomerNo, h.PROJECTID AS ProjectID, h.AMOUNT AS Amount

On one hand, I can't say "just add one", because clearly sometimes they don't want to add one. On the other hand, there's an element of looking at this and knowing: well, something absolutely stupid has happened here. Maybe it was two disjoint databases getting merged. Maybe it was just once upon a time, when this database was a spreadsheet, the user responsible did a weird thing. Maybe some directive changed the document type numbering. Hell, maybe that ELSE clause never gets triggered, and we actually could just do arithmetic.

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