Translating a query from MS Access to SQL Server I have a legacy query from years ago that was written for an MS Access backend:

    DELETE category.*
    FROM category
    LEFT JOIN product_category ON category.id = product_category.categoryid
    WHERE product_category.categoryid IS NULL
      AND category.id IN
        (SELECT cat.id
         FROM category AS cat
         LEFT JOIN category AS cat_par ON cat_par.category_parent = cat.id
         WHERE cat_par.category_parent IS NULL
           AND cat.category_parent != 0
           AND cat.link IS NULL);


My system was changed to SQL Server and this query no longer runs.
I have tested the subquery (in the parenthesis) separately and that works as expected. Just no records are getting deleted.

I have tried changing  the first two lines to read DELETE FROM category (the only syntax difference I was able to look up) but still no deletion occurs.
I think Binaya Regmi is correct. When deleting in SQL-Server explicitly name the table you want to delete the rows from - especially necessary when using a join. 

So in your case change the top row from 

DELETE category.*


to

DELETE category