SQL 更改查询以显示孤儿

Question

给出查询：

SELECT
    tblProducts.ID, tblProducts.views, tblProducts.productName, tblProducts.isForSale, tblProducts.isLimitedStock, tblProducts.stockCount, tblProducts.description, tblProducts.weightKG, tblProducts.basePrice, tblProducts.dateCreated, tblProductCats.catName, 
    (SELECT COUNT(*) FROM tblProductPrices WHERE productId = tblproducts.id) AS priceMods, 
    (SELECT COUNT(*) FROM tblcomments WHERE productId = tblproducts.ID) AS comments,
    (SELECT COUNT(*) FROM tblProductImages WHERE productID = tblproducts.id) AS imageCount
FROM
    tblProducts
INNER JOIN
    tblProductCats ON tblProducts.categoryID = tblProductCats.ID

如果产品的类别 ID 为 0 (tblProducts INNER JOIN tblProductCats ON tblProducts.categoryID = tblProductCats.ID) 它不会返回产品记录，是否可以修改查询使其返回值为 0 的记录并将类别名称显示为“孤儿”？

Answer 1

SELECT ...
       ISNULL(tblProductCats.catName,'Orphan') AS  catName   ,
/*
Or possibly...
       CASE
              WHEN tblProducts.categoryID = 0
              THEN 'Orphan'
              ELSE tblProductCats.catName
       END AS catName
       */
       ...
FROM   tblProducts
       LEFT OUTER JOIN tblProductCats
       ON     tblProducts.categoryID = tblProductCats.ID