case表达式

 1 SELECT productid, productname, categoryid,  2   CASE categoryid  3     WHEN 1 THEN 'Beverages'

 4     WHEN 2 THEN 'Condiments'

 5     WHEN 3 THEN 'Confections'

 6     WHEN 4 THEN 'Dairy Products'

 7     WHEN 5 THEN 'Grains/Cereals'

 8     WHEN 6 THEN 'Meat/Poultry'

 9     WHEN 7 THEN 'Produce'

10     WHEN 8 THEN 'Seafood'

11     ELSE 'Unknown Category'

12   END AS categoryname 13 FROM Production.Products;

输出结果为：

 

对Sales.OrderValues视图的查询先根据val的逻辑顺序生成3个组，再把组的编号翻译成组的描述信息(Low、Medium、High)：

1 SELECT orderid, custid, val,

2   CASE NTILE(3) OVER(ORDER BY val)

3     WHEN 1 THEN 'Low'

4     WHEN 2 THEN 'Medium'

5     WHEN 3 THEN 'High'

6     ELSE 'Unknown'

7   END AS titledesc

8 FROM Sales.OrderValues

9 ORDER BY val;

 

查询结果如下：