全外连接 - 交织值从联接的列

Question

对于纯粹的教育目的，我应该怎么写，而不是*这样，我得到同来自weather.city或city.name值只有一列city_name，两者存在？

flav=# select * from weather full outer join cities on weather.city = cities.name; 
    city  | temp_lo | temp_hi | prcp | date |  name  | location 
---------------+---------+---------+------+------------+---------------+----------- 
San Francisco |  46 |  50 | 0.25 | 1994-11-27 | San Francisco | (-194,53) 
San Francisco |  43 |  57 | 0 | 1994-11-29 | San Francisco | (-194,53) 
Hayward  |  37 |  54 |  | 1994-11-29 |    | 
       |   |   |  |   | Graz   | (90,-90) 

Answer 1

发现：

SELECT COALESCE(city, name) AS city_name ...