SELECT
c1.Name,
c2.Population
FROM country AS c1, country AS c2
WHERE
c1.Code = c2.Code
| Name | Population |
| Aruba | 103,000 |
| Afghanistan | 22,720,000 |
| Angola | 12,878,000 |
| Anguilla | 8,000 |
| Albania | 3,401,200 |
| Andorra | 78,000 |
| Netherlands Antilles | 217,000 |
| United Arab Emirates | 2,441,000 |
| Argentina | 37,032,000 |
| ... |
| country 第一次出现时取别名 C1，第二次取别名 C2。之后就可以把这两个别名当作表名使用。 |