Traffic Light system for warranties in a MYSQL Database - mysql

Question

I have a table of printers with a warranty start and warrant end date stored as a date field in our MYSQL database
I want to visualise the warranty end dates using the current date as a traffic lights system
Red - warranties ended
Amber - warranties ending within 90 days
Green - warranties that end in more than 90 days
Example data
+--------------------------------------+-----------------+---------------+
| id | warrantystart_c | warrantyend_c |
+--------------------------------------+-----------------+---------------+
| 001c28c4-b9cf-11e9-88a2-020683bef092 | 2018-07-13 | 2020-07-12 |
| 453b9ba2-b9ce-11e9-8fd6-0265ed7510c2 | 2018-09-26 | 2020-09-25 |
| 5c8353e2-0585-11ea-bbe5-066c2def7d44 | 2018-09-26 | 2020-09-25 |
| 71F1934 | 2018-08-28 | 2020-08-27 |
| 71F1936 | 2018-08-28 | 2020-08-27 |
| 71F2367 | 2018-09-03 | 2020-09-02 |
| 001c28c4-b9cf-11e9-88a2-020683bef092 | 2018-07-13 | 2020-07-12 |
| 0024d2ca-fb2f-11e9-8fcc-0265ed7510c2 | 2019-08-20 | 2022-08-19 |
| 00514c1c-6a5a-11e9-9026-0265ed7510c2 | 2019-04-18 | 2022-04-17 |
| 00613772-bdc4-11e9-8c8f-0265ed7510c2 | 2019-07-01 | 2022-06-30 |
| 006ac524-ef5d-11e9-b323-020683bef092 | 2019-09-30 | 2022-09-29 |
| 006b3ea2-e911-11e9-8ab6-0265ed7510c2 | 2019-10-07 | 2022-10-06 |
| 008fb146-f501-11e9-9875-06a63d65978a | 2018-02-14 | 2021-02-13 |
| 0130078c-d2ff-11e9-96e7-06a63d65978a | 2019-08-23 | 2022-08-22 |
| 0180c41e-bf5a-11e9-8abf-06a63d65978a | 2019-07-25 | 2022-07-24 |
| 0279f4ce-bdc2-11e9-ac0d-020683bef092 | 2019-07-01 | 2022-06-30 |
| 002f826c-c7cf-11e9-9104-0265ed7510c2 | NULL | 1969-12-31 |
| 031b46b4-113f-11ea-80e4-020683bef092 | 2014-07-10 | 2017-07-09 |
| 0af91f74-52da-11e9-947b-0265ed7510c2 | 2019-04-01 | 2019-04-30 |
| 0c89a096-f5bb-11e9-9313-066c2def7d44 | 1900-01-02 | 1905-01-01 |
+--------------------------------------+-----------------+---------------+
from this table the result I'm looking to get is
+-----+-------+-------+--+
| Red | amber | green | |
+-----+-------+-------+--+
| 4 | 6 | 10 | |
+-----+-------+-------+--+
I have tried three WHERE clauses to get this data
snc.warrantyend_c < current_date // Red
snc.warrantyend_c BETWEEN CURDATE() and DATE_ADD(CURDATE(), INTERVAL 90 DAY) // Amber
snc.warrantyend_c > subdate(current_date, INTERVAL 90 DAY) // Green
I just wandered if there's a better way to do the where clauses and an efficient way to do this all in one query or should I use sub queries?

Answer 1

You can aggregate and sum() the expressions for the different colors. This works as Boolean expressions in numeric context are interpreted as 1 for true and 0 for false in MySQL.
SELECT sum(snc.warrantyend_c < current_date) red,
sum(snc.warrantyend_c BETWEEN current_date and date_add(current_date, INTERVAL 90 DAY)) amber,
sum(snc.warrantyend_c > subdate(current_date, INTERVAL 90 DAY)) green
FROM elbat snc;

Answer 2

You're correct that your existing individual queries will get you the data you need:
SELECT COUNT(*) as red FROM warrantiesWHERE end < current_date;
SELECT COUNT(*) as yellow FROM warranties WHERE end BETWEEN CURDATE() and DATE_ADD(CURDATE(), INTERVAL 90 DAY);
SELECT COUNT(*) as green FROM warrantiesWHERE end > subdate(current_date, INTERVAL 90 DAY);
But these can be combined with a CASE statement as a separate column:
SELECT
*,
CASE
WHEN end < current_date THEN 'red'
WHEN end BETWEEN CURDATE() and DATE_ADD(CURDATE(), INTERVAL 90 DAY) THEN 'yellow'
WHEN end > subdate(current_date, INTERVAL 90 DAY) THEN 'green'
END as color
FROM warranties;
And then finally you can use GROUP BY on this query to get the counts:
SELECT
color,
COUNT(*) as count
FROM (
SELECT
*,
CASE
WHEN end < current_date THEN 'red'
WHEN end BETWEEN CURDATE() and DATE_ADD(CURDATE(), INTERVAL 90 DAY) THEN 'yellow'
WHEN end > subdate(current_date, INTERVAL 90 DAY) THEN 'green'
END as color
FROM warranties
) colors
GROUP BY color;
Working example at http://sqlfiddle.com/#!9/aed6cd/2

Answer 3

Thanks for you help and I'm working through some lessons to learn more about the points raised. I've used this to create the full statement
SELECT
color,
COUNT(*) AS count
FROM (
SELECT
sn.id,
CASE
WHEN snc.warrantyend_c < current_date THEN 'red'
WHEN snc.warrantyend_c BETWEEN CURDATE() and DATE_ADD(CURDATE(), INTERVAL 90 DAY) THEN 'amber'
WHEN snc.warrantyend_c > subdate(current_date, INTERVAL 90 DAY) THEN 'green'
END AS color
FROM
s_serialnumber sn
LEFT JOIN s_serialnumber_cstm snc ON sn.id = snc.id_c
WHERE
snc.dealer_id_c = "1000521"
) colors
GROUP BY color;