This example provides sample configuration for creating a mysql or postgres instance. For Oracle/SQL Servers, replace default values with appropriate values, they are not included in sample since the number of options are high.
If you need to use existing security groups and subnets, remove the `sg.tf` and `subnets.tf` files and replace the corresponding sections in `main.tf` under `aws_db_instance`
Several parameters are externalized, review the different variables.tf files and change them to fit your needs. Carefully review the CIDR blocks, egress/ingress rules, availability zones that are very specific to your account.