Join型代理是在几个类的连接结果上进行代理。它可以达到类似于“多继承”的表现效果。一个代理对象在 每个源类中都对应一个源对象。 例子:创建一个代理类assistant存储所有学生(既是学生又是老师)的信息。 CREATE JOINDEPUTYCLASS assistant AS ( SELECT student.name, salary FROM student,faculty WHERE student.id = faculty.id );
数据库运行错误2021/2/4 11:05:58 (余伟)
createdb: could not connect to database totem: could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
请问如何定义Join代理类
Join型代理是在几个类的连接结果上进行代理。它可以达到类似于“多继承”的表现效果。一个代理对象在
每个源类中都对应一个源对象。
例子:创建一个代理类assistant存储所有学生(既是学生又是老师)的信息。
CREATE JOINDEPUTYCLASS assistant
AS
( SELECT student.name, salary FROM student,faculty
WHERE student.id = faculty.id );
createdb: could not connect to database totem: could not connect to server:
No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
这意味着该服务器没有启动,或者没有在createdb预期的地方启动。同样,你也要检查安装指导或者找管理员。