Closing percent MATH in MYSQL - php

Question

I want to do math in a query, and was wondering if its better to do it in PHP or MYSQL.
Also, if I choose MYSQL can anyone help me with the query.
So far I have
SELECT COUNT(*) as total, booker, appdate,
SUM(CASE WHEN status='DNS' THEN 1 ELSE 0 END) book,
SUM(CASE WHEN status!='DNS' THEN 1 ELSE 0 END) tot
FROM appts WHERE WEEK(app_date)= WEEK(CURDATE()) GROUP BY booker
I want one more stat from this query.
I want to do book / (book+tot)
But obviously only if book!=0 or tot!=0, since obviously I don't want to divide anything by zero.
Is there a way to do this in a MYSQL query??
I want my output to be.....
book | 14
tot | 25
hold | 35%
Id also like to ORDER BY the hold percent from highest to lowest. Is this possible????

Answer 1

You can achieve what you ask for using a subquery, like this:
SELECT *, IF(book + tot, 100*book/(book + tot), NULL) AS hold
FROM (
SELECT COUNT(*) as total, booker, appdate,
SUM(status='DNS') book, SUM(status!='DNS') tot
FROM appts WHERE WEEK(app_date)= WEEK(CURDATE()) GROUP BY booker
) AS subquery
ORDER BY hold DESC
Note that in several places I'm using the fact that MySQL uses numbers for logical values. So you can sum up conditions without CASE, and you can write a formula for IF without <> 0 check.

Answer 2

Naive method:
SELECT
COUNT(*) as total,
SUM(CASE WHEN status='DNS' THEN 1 ELSE 0 END) book,
SUM(CASE WHEN status!='DNS' THEN 1 ELSE 0 END) tot,
IF( ( SUM(CASE WHEN status!='DNS' THEN 1 ELSE 0 END) +
SUM(CASE WHEN status='DNS' THEN 1 ELSE 0 END) ) = 0,
0,
SUM(CASE WHEN status='DNS' THEN 1 ELSE 0 END) /
( SUM(CASE WHEN status!='DNS' THEN 1 ELSE 0 END) +
SUM(CASE WHEN status='DNS' THEN 1 ELSE 0 END) )
) AS hold
FROM appts
WHERE WEEK(app_date) = WEEK(CURDATE()) GROUP BY booker
ORDER BY hold;
Or in order not to repeat your aliases, use a subquery:
SELECT *, IF (book + tot = 0, 0, book / (book + tot) * 100)
FROM (
SELECT
COUNT(*) as total,
SUM(CASE WHEN status='DNS' THEN 1 ELSE 0 END) book,
SUM(CASE WHEN status!='DNS' THEN 1 ELSE 0 END) tot,
FROM appts
WHERE WEEK(app_date) = WEEK(CURDATE()) GROUP BY booker
) AS subq
ORDER BY hold;
Or, more cleverly :) (book + tot = total)
SELECT *, IF (total = 0, 0, book / total * 100)
FROM (
SELECT
COUNT(*) as total,
SUM(CASE WHEN status='DNS' THEN 1 ELSE 0 END) book,
SUM(CASE WHEN status!='DNS' THEN 1 ELSE 0 END) tot,
FROM appts
WHERE WEEK(app_date) = WEEK(CURDATE()) GROUP BY booker
) AS subq
ORDER BY hold;
And, just for fun, the hackishly compactest form:
SELECT *, COALESCE(book / total * 100, 0) AS hold -- a division by 0 returns NULL
FROM (
SELECT
COUNT(*) total,
SUM(status='DNS') book, -- boolean "true" is internally integer "1"
SUM(status!='DNS') tot,
FROM appts
WHERE WEEK(app_date) = WEEK(CURDATE()) GROUP BY booker
) AS subq
ORDER BY hold;