基础篇-组合查询 Combining Queries

Using UNION 全部合并去重复

SELECT Name, Population, SurfaceArea 
FROM country
WHERE Population > 200000000
UNION
SELECT Name, Population, SurfaceArea 
FROM country
WHERE SurfaceArea > 9000000

Using UNION ALL 全部合并

SELECT Name, Population, SurfaceArea 
FROM country
WHERE Population > 200000000
UNION ALL
SELECT Name, Population, SurfaceArea 
FROM country
WHERE SurfaceArea > 9000000

Sorting Combined Query Results 合并结果排序

SELECT Name, Population, SurfaceArea 
FROM country
WHERE Population > 200000000
UNION ALL
SELECT Name, Population, SurfaceArea 
FROM country
WHERE SurfaceArea > 9000000
ORDER BY Name