End play if database does not exits - ansible

Question

I have created the following playbook, to check if a database exists:
- name: Check database exits
shell: |
mysql -hmysqlhost -uroot -ppassword -e "show databases" | egrep db"
register: mysql_exist
- name: Show database
debug:
msg: "{{ mysql_exist.stdout }}"
My idea is to finish the playbook if the database does not exist and show a message, I tried this but it does not work, otherwise I should continue to the next task.
- name: Check database exits
shell: |
mysql -hmysqlhost -uroot -ppassword -e "show databases" | egrep db"
register: mysql_exist
- name: End Playbook If database not exits.
meta: end_play
when: mysql_exist == 0
- name: Show database
debug:
msg: "{{ mysql_exist.stdout }}"
## other tasks
How can I create a playbook to check if a database exists and if it does not exist, it must display the message The database does not exist and finish the playbook without running other tasks?

Answer 1

if you want to show a message if playbook has to finish, use a block:
(you dont show the output of your register when a db doesnt exist so, i suppose your test in when condition is ok!!)
- block:
- name: "end play "
debug:
msg: "db doesnt exist"
- meta: end_play
when: mysql_exist == 0
so the playbook is finished after the message displaying

Answer 2

Do you need to show the message? Stopping the playbook already happens automatically if egrep does not find anything, because it exits with a non-0 code.
Playbook:
---
- hosts: srv1
become: True
tasks:
- name: x
shell: "echo nope | egrep dbname"
- name: good
shell: "echo very much"
Output (notice how "good" is not executed):
PLAY [srv1] *******************************************************************************************************************************
TASK [x] **********************************************************************************************************************************
fatal: [srv1]: FAILED! => {"changed": true, "cmd": "echo nope | egrep dbname", "delta": "0:00:00.005942", "end": "2022-02-09 15:56:56.726828", "msg": "non-zero return code", "rc": 1, "start": "2022-02-09 15:56:56.720886", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}
PLAY RECAP ********************************************************************************************************************************
srv1 : ok=0 changed=0 unreachable=0 failed=1 skipped=0 rescued=0 ignored=0
It could be approximated with something like this:
- name: x
shell: "echo nope | egrep dbname || { echo Database not found && false; }"
Which gives:
TASK [x] ***********************************************************************************************************************************
fatal: [srv1]: FAILED! => {"changed": true, "cmd": "echo nope | egrep dbname || { echo Database not found && false; }", "delta": "0:00:00.006159", "end": "2022-02-09 15:59:26.176704", "msg": "non-zero return code", "rc": 1, "start": "2022-02-09 15:59:26.170545", "stderr": "", "stderr_lines": [], "stdout": "Database not found", "stdout_lines": ["Database not found"]}