SQL-如何在SQL VIEW中添加列，但不将其添加或更新到表中？

Question

如何在“美国”，“亚洲”，“亚洲”，“亚洲”等“ SQL THAT LIST USA”中添加列，而无需在表中实际添加数据，而仅将其包括在视图中。 我想同时包括COUNTRY_VISITED和名为CONTINENTS的新列。

CREATE OR REPLACE VIEW V_HOLIDAYS 
AS
    SELECT CODE_OF_HOLIDAY, DESCRIPTION, COUNTRY_VISITED
    FROM ZZZ_HOLIDAY_DETAILS;    

Answer 1

CREATE OR REPLACE VIEW V_HOLIDAYS AS
SELECT  CODE_OF_HOLIDAY, 
        DESCRIPTION, 
        case when COUNTRY_VISITED = 'USA' then 'America'
             when COUNTRY_VISITED in ('India','China') then 'Asia'
             else COUNTRY_VISITED 
        end as COUNTRY_VISITED 
FROM ZZZ_HOLIDAY_DETAILS;  

Answer 2

使用case声明：

CREATE OR REPLACE VIEW V_HOLIDAYS 
AS
    SELECT CODE_OF_HOLIDAY, DESCRIPTION, COUNTRY_VISITED,
           (CASE WHEN COUNTRY_VISITED = 'USA' THEN 'AMERICA'
                 WHEN COUNTRY_VISITED IN ('INDIA', 'CHINA') THEN 'ASIA'
            END) as CONTINENT
    FROM ZZZ_HOLIDAY_DETAILS;    

Answer 3

 SELECT CODE_OF_HOLIDAY, DESCRIPTION, COUNTRY_VISITED, 
 CASE WHEN COUNTRY_VISITED = 'USA' THEN 'America' 
      WHEN COUNTRY_VISITED = 'China' THEN 'Asia' 
      WHEN COUNTRY_VISITED = 'India' THEN 'Asia' ELSE COUNTRY_VISITED 
 END AS COUNTRY_VISITED_ALIAS
 FROM ZZZ_HOLIDAY_DETAILS