SQL工作从左到右直到找到值

Question

I've been scratching my head at this but cannot find an 'elegant' way to do it. I'm using MS SQL Server 2012.

Basically, I'm been given a table (ItemsBySeason) that contains a bunch of items. The length of the actual items will either be 11 (planning entity) or 7 (style) characters in length.

I then have another table (PriceLists) with items and prices. Again these have items with a price, and the items will be both 7 and 11 characters on length.

My question is, is there a function out there that would read through each item in ItemBySeason and check if there is a price in the PriceLists table that matches at 11 characters in length, if not then use the price for the 7 character item?

For example:

Table: Item By Season
Item: AABBCCD1234

Table: PriceLists
Item: AABBCCD1234
Price: 10

So in this instance it would I could retrieve the 10 for AABBCCD1234

However, if the below happened:

Table: Item By Season
Item: AABBCCD8888

No match for 'AABBCCD8888' in PriceLists but the below exists:

Table: PriceLists
Item: AABBCCD
Price: 12

How do I check that the 7 length exists and pull through 12?

Any help would be greatly appreciated. The only work around I've found is to create a temp table of every single Item that doesn't have a price at the planning entity level and bring all those through at the style level, then append to the PriceLists table, but this seems long winded.

Thanks,

Michael

Answer 1

SELECT item_by_season.item
     , planning_entity_prices.price A planning_entity_price
     , style_prices.price As style_price
     , Coalesce(planning_entity_prices.price, style_prices.price) As price
FROM   item_by_season
 LEFT
  JOIN price_lists As planning_entity_prices
    ON planning_entity_prices.item = item_by_season.item
   AND Len(planning_entity_prices.item) = 11
 LEFT
  JOIN price_lists As style_prices
    ON style_prices.item = item_by_season.item
   AND Len(style_prices.item) = 7
;

Answer 2

Here is a method that uses a correlated subquery (or equivalently it could use cross apply ). If something matches both the 7 and 11 length strings, it chooses the one with 11.

select i.*,
       (select top 1 pl.price
        from PriceLists pl
        where pl.itemid = i.itemid or
              left(i.itemid, 7) = pl.itemid
        order by len(pl.itemid) desc
       ) as price
from ItemsBySeason i ;