Output a ratio and the percentage (as a string?)

I have successfully calculated a value I want from a database. I now want to take that value, put it over the total number from the table I'm looking at (to get the ratio) and also output the percentage. I'm not quite sure if I need to convert those to strings to output them, or some other method? I would love some help.

This is the code I have so far to calculate the value I want in the numerator, but I'm not sure how to combine the denominator (I imagine I'll have to use some sort of COUNT command).

use rt_database;
DELIMITER //
CREATE PROCEDURE Generate_Relationship_Ubiquity()
BEGIN
    DECLARE Desired_Relationship VARCHAR (20);
    SET Desired_Relationship = 'RS-008';
    
	SELECT COUNT(DISTINCT statements.`Source ID`) AS "Relationship Ubiquity Count" 
    FROM observations
    INNER JOIN statements ON observations.`Statement ID` = statements.`Statement ID`
    WHERE observations.`Relationship ID` = Desired_Relationship;
END;
//
DELIMITER ;
CALL Generate_Relationship_Ubiquity;
DROP PROCEDURE Generate_Relationship_Ubiquity;

You just need a subquery without the where condition to get the total:

SELECT COUNT(DISTINCT statements.`Source ID`)
    / (select count(distinct statements.`Source ID`) from observations join statements using(`Statement ID`)) ubiquity_ratio
FROM observations...

If you need the total more than once (to return it separately as well as the ratio, or to return both a ratio and a percentage), put the subquery in a common table expression:

WITH total_distinct_sources AS (select count(distinct statements.`Source ID`) as sources from observations join statements using(`Statement ID`))
SELECT
    total_distinct_sources.sources total_ubiquity,
    COUNT(DISTINCT statements.`Source ID`) "Relationship Ubiquity Count",
    COUNT(DISTINCT statements.`Source ID`) / total_distinct_sources.sources ubiquity_ratio,
    100 * COUNT(DISTINCT statements.`Source ID`) / total_distinct_sources.sources ubiquity_percent
FROM total_distinct_sources
CROSS JOIN observations
INNER JOIN statements ON observations.`Statement ID` = statements.`Statement ID`
WHERE observations.`Relationship ID` = Desired_Relationship;