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+1 A:

Note that the lang is defined on the JOIN

   SELECT COALESCE(pd.short_description, t.short_description)
     FROM PRODUCT_DESCRIPTIONS t
LEFT JOIN PRODUCT_DESCRIPTIONS pd ON pd.product_id = t.product_id 
                                 AND pd.lang = 'mk'
    WHERE t.is_default = 1

It won't work if you filter the language in the WHERE clause.

OMG Ponies 2009-08-31 22:16:44

+1 assuming there is a *is_default* label for every product id. Otherwise I would start with (FROM) the desired language left-joining on the default (and specifying the t.is_default as another condition of the JOIN rather then in WHERE clause)

van 2009-08-31 22:32:02

@van: You can't start with the desired language - you wouldn't get the product_ids where the desired language doesn't exist, so it'd be worthless to try to get the default language short_description value.

OMG Ponies 2009-08-31 23:22:31

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SQL query: Listing product descriptions

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