PostgreSQL 子查询字段: SELECT name,(select cn from city where id=s.id) as icn from scenic as s 如果子查询没有值，则icn显示为Null，如何不显示为Null?

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PostgreSQL 子查询字段: SELECT name,(select cn from city where id=s.id) as icn from scenic as s 如果子查询没有值，则icn显示为Null，如何不显示为Null?

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COALESCE了解一下，coalesce(a,b)，a为空显示b，a不为空显示a

SELECT name,COALESCE((select cn from city where id=s.id),'Null') as icn from scenic as s;--子查询为空时显示null

SELECT name,COALESCE((select cn from city where id=s.id),'1234') as icn from scenic as s;--子查询为空时显示1234

SELECT name,COALESCE((select cn from city where id=s.id),'1234') as icn from scenic as s;--子查询不为空时显示cn值

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SELECT name,
coalesce((select cn from city where id=s.id),'') as icn 
from scenic as s

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