mysql error

ubuntu@ubuntu:~$ sudo apt install mysql-client-core-5.7
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  libaio1
The following NEW packages will be installed:
  libaio1 mysql-client-core-5.7
0 upgraded, 2 newly installed, 0 to remove and 267 not upgraded.
Need to get 7,409 kB of archives.
After this operation, 34.5 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://security.ubuntu.com/ubuntu zesty-security/main amd64 mysql-client-core-5.7 amd64 5.7.19-0ubuntu0.17.04.1 [7,403 kB]
Get:2 http://archive.ubuntu.com/ubuntu zesty/main amd64 libaio1 amd64 0.3.110-3 [6,382 B]
19% [1 mysql-client-core-5.7 811 kB/7,403 kB 11%]            92.8 kB/s 1min 1119% [1 mysql-client-core-5.7 857 kB/7,403 kB 12%]          92.8 kB/s 1min 10Fetched 7,409 kB in 1min 3s (117 kB/s)
Selecting previously unselected package libaio1:amd64.
(Reading database ... 186465 files and directories currently installed.)
Preparing to unpack .../libaio1_0.3.110-3_amd64.deb ...
Unpacking libaio1:amd64 (0.3.110-3) ...
Selecting previously unselected package mysql-client-core-5.7.
Preparing to unpack .../mysql-client-core-5.7_5.7.19-0ubuntu0.17.04.1_amd64.deb ...
Unpacking mysql-client-core-5.7 (5.7.19-0ubuntu0.17.04.1) ...
Processing triggers for libc-bin (2.24-9ubuntu2) ...
Setting up libaio1:amd64 (0.3.110-3) ...
Processing triggers for man-db (2.7.6.1-2) ...
Setting up mysql-client-core-5.7 (5.7.19-0ubuntu0.17.04.1) ...
Processing triggers for libc-bin (2.24-9ubuntu2) ...
ubuntu@ubuntu:~$ mysql
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
ubuntu@ubuntu:~$