CASE 语句

--简单case函数

USE pubs
GO
SELECT   Category =
      CASE type
         WHEN 'popular_comp' THEN '计算机类'
         WHEN 'mod_cook' THEN '现代厨艺'
         WHEN 'business' THEN '商业图书'
         WHEN 'psychology' THEN '心理学'
         WHEN 'trad_cook' THEN '传统厨艺'
         ELSE '未分类'
      END,
   avg(price) AS 'Average Price'
FROM titles
WHERE price IS NOT NULL
GROUP BY type
ORDER BY type
GO

--case搜索函数
USE pubs
GO
SELECT    title ,
 'Price Category' =
      CASE
         WHEN price IS NULL THEN '未定价'
         WHEN price < 10 THEN '价格小于10美元'
         WHEN price >= 10 and price < 20 THEN '价格介于10到20美元之间'
         ELSE '高于20美元'
      END 
FROM titles
ORDER BY price
GO