MySQL sum of a calculation error - mysql

Question

I'm struggling with calculating the sum of another calculation in MySQL Workbench. I don't really know how to explain it in words, so I'll provide some data.
Here I have tables and data:
drop database if exists GDPR;
create database if not exists GDPR;
use GDPR;
drop table if exists Company;
create table Company
(
id_company int not null auto_increment,
name varchar (50),
primary key (id_company)
) auto_increment = 1;
drop table if exists GDPR_steps;
create table GDPR_steps
(
id_step int not null auto_increment,
id_company int,
name varchar (50),
primary key (id_step),
foreign key (id_company) references Company (id_company)
) auto_increment = 1;
drop table if exists compliance;
create table compliance
(
id_com int not null auto_increment,
id_step int,
initiative varchar (50),
status varchar (10),
primary key (id_com),
foreign key (id_step) references gdpr_steps (id_step)
) auto_increment = 1;
insert into company
values (null, 'Mango'), (null, 'Kiwi');
insert into gdpr_steps
values (null, 1, 'Awareness'), (null, 1, 'Information you hold'),
(null, 2, 'Awareness'), (null, 2, 'Information you hold');
insert into compliance
values (null, 1, 'E-mail all employees', '1'),
(null, 1, 'E-mail all applicants', '0'),
(null, 2, 'Delete some data', '1'),
(null, 3, 'Call stakeholders', '1'),
(null, 4, 'Review data', '0');
I have this query which calculates the ratio of completion for each step by each company based on the status of each of the initiatives belonging to a certain step.
select
company.name as 'Company',
gdpr_steps.name as 'ID Step',
(sum(compliance.status)/count(compliance.status)) * 100 as 'Ratio %'
from
compliance, company, gdpr_steps
where
gdpr_steps.id_step = compliance.id_step
and company.id_company = gdpr_steps.id_company
group by
compliance.id_step, company.id_company;
The query above returns this output:
Company ID Step Ratio %
-----------------------------------------
Mango Awareness 50
Mango Information you hold 100
Kiwi Awareness 100
Kiwi Information you hold 0
Now, when I want to calculate the ratio per company (eg. summing the ratio from step1 with the one from step2 and divide it by 2) I can't make it work. Which would be like
Company Overall ratio %
Mango (Awareness (50) + Information you hold (100)) / nr of steps (2 in our case)
Kiwi (Awareness (0) + Information you hold (100)) / nr of steps (2 in our case)
Which in our case would result in something like:
Name Overall ratio %
Mango 75
Kiwi 50
I have tried something like
select
company.name,
((sum(compliance.status)/count(compliance.status)) * 100)/ count(gdpr_steps.id_step)
from
compliance, company, gdpr_steps
where
gdpr_steps.id_step = compliance.id_step
and company.id_company = gdpr_steps.id_company
group by
company.id_company;
This one doesn't seem to work at all, as I receive totally different values than expected.
Could you please explain me what I got wrong?
Kind regards!

Answer 1

It seems like you're after the following...
SELECT company
, AVG(`ratio %`) n
FROM
(
-- your query here --
) x
GROUP
BY company;