add documentation/sample for checkmode

Author: elmarx

README.md

@@ -24,6 +24,7 @@ Example playbook
 ### A complete example that ensures a record is present in a given table.
 
 ```yaml
+
 ---
 - hosts: all
   roles:
@@ -60,6 +61,7 @@ Thus:
 ### A complete example that ensures a record is not present in a given table.
 
 ```yaml
+
 ---
 - hosts: all
   roles:
@@ -83,3 +85,6 @@ Thus:
 Make sure you have a running mysql server (e.g.: use the *docker-compose.yml*-file) and update the connection-parameters if necessary.
 
 Run via `ansible-playbook -i demo.yml` (or even simpler `./demo.yml`) and undo (to start all over) with `ansible-playbook -i reset.yml`.
+
+After running `./demo.yml`, you can run `./checkmode-demo.yml -C` to test ansible's [check mode](https://docs.ansible.com/ansible/latest/user_guide/playbooks_checkmode.html).
+Just run `./demo.yml` and `./checkmode-demo.yml` a few times with `-C` and without `-C` to get a feel for it.

examples/checkmode-demo.yml

@@ -0,0 +1,38 @@
+#!/usr/bin/env ansible-playbook
+---
+- hosts: all
+  gather_facts: no
+  tasks:
+    - name: update a row
+      mysql_query:
+        name: ansible-playbook-example
+        table: simple_table
+        login_host: ::1
+        login_user: root
+        login_password: password
+        identifiers:
+          identifier1: 4
+          identifier2: 'eight'
+        values:
+          value1: 42
+          value2: 'myvalue'
+        defaults:
+          default1: can be anything, will be ignored for update
+          default2: will not change
+
+    - name: insert a row
+      mysql_query:
+        name: ansible-playbook-example
+        table: simple_table
+        login_host: ::1
+        login_user: root
+        login_password: password
+        identifiers:
+          identifier1: 14
+          identifier2: 'eighteen'
+        values:
+          value1: 115
+          value2: 'one-hundred-sixteen'
+        defaults:
+          default1: 125
+          default2: one-hundred-25