打字sudo apt-get install postgresql-11给我错误：
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
postgresql-11 : Depends: postgresql-client-11
Depends: libicu55 (>= 55.1-1~) but it is not installable
Depends: libpq5 (>= 9.3~) but it is not going to be installed
Depends: libssl1.0.0 (>= 1.0.2~beta3) but it is not installable
Recommends: sysstat but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
如何解决此错误并最终在我的ubuntu上安装Postgres？
sudo apt-get update
sudo apt-get install postgresql postgresql-contrib
尝试运行该命令，让我知道你看到了什么。显然，postgres需要一些尚未安装的软件包