How can I make this SQL query more elegant? - mysql

Question

This is my MySQL query for getting count values...
SELECT 1 AS id,
'2016' AS Year,
MAX( IF( Month = '01', Count, 0 ) ) AS 'VAL01',
MAX( IF( Month = '02', Count, 0 ) ) AS 'VAL02',
MAX( IF( Month = '03', Count, 0 ) ) AS 'VAL03',
MAX( IF( Month = '04', Count, 0 ) ) AS 'VAL04',
MAX( IF( Month = '05', Count, 0 ) ) AS 'VAL05',
MAX( IF( Month = '06', Count, 0 ) ) AS 'VAL06',
MAX( IF( Month = '07', Count, 0 ) ) AS 'VAL07',
MAX( IF( Month = '08', Count, 0 ) ) AS 'VAL08',
MAX( IF( Month = '09', Count, 0 ) ) AS 'VAL09',
MAX( IF( Month = '10', Count, 0 ) ) AS 'VAL10',
MAX( IF( Month = '11', Count, 0 ) ) AS 'VAL11',
MAX( IF( Month = '12', Count, 0 ) ) AS 'VAL12',
SUM( Count ) AS Total
FROM ( SELECT DATE_FORMAT( created_at, '%m' ) AS Month,
COUNT( 1 ) AS Count
FROM reservations
WHERE DATE_FORMAT( created_at, '%Y' ) = '2016'
GROUP BY DATE_FORMAT( created_at, '%m' )
) AS T1
UNION
SELECT 2 AS id,
'2017' AS Year,
MAX( IF( Month = '01', Count, 0 ) ) AS 'VAL01',
MAX( IF( Month = '02', Count, 0 ) ) AS 'VAL02',
MAX( IF( Month = '03', Count, 0 ) ) AS 'VAL03',
MAX( IF( Month = '04', Count, 0 ) ) AS 'VAL04',
MAX( IF( Month = '05', Count, 0 ) ) AS 'VAL05',
MAX( IF( Month = '06', Count, 0 ) ) AS 'VAL06',
MAX( IF( Month = '07', Count, 0 ) ) AS 'VAL07',
MAX( IF( Month = '08', Count, 0 ) ) AS 'VAL08',
MAX( IF( Month = '09', Count, 0 ) ) AS 'VAL09',
MAX( IF( Month = '10', Count, 0 ) ) AS 'VAL10',
MAX( IF( Month = '11', Count, 0 ) ) AS 'VAL11',
MAX( IF( Month = '12', Count, 0 ) ) AS 'VAL12',
SUM( Count ) AS Total
FROM ( SELECT DATE_FORMAT( created_at, '%m' ) AS Month,
COUNT( 1 ) AS Count
FROM reservations
WHERE DATE_FORMAT( created_at, '%Y' ) = '2017'
GROUP BY DATE_FORMAT( created_at, '%m' )
) AS T2
It returns (for example)...
+----+------+-------+-------+-------+-------+-------+-------+-----+-------+-------+
| id | Year | VAL01 | VAL02 | VAL03 | VAL04 | VAL05 | VAL06 | ... | VAL12 | Total |
+----+------+-------+-------+-------+-------+-------+-------+-----+-------+-------+
| 1 | 2016 | 0 | 0 | 150 | 190 | 200 | 220 | ... | 160 | 1242 |
+----+------+-------+-------+-------+-------+-------+-------+-----+-------+-------+
| 2 | 2017 | 300 | 300 | 600 | 600 | 700 | 0 | ... | 0 | 2500 |
+----+------+-------+-------+-------+-------+-------+-------+-----+-------+-------+
My query has many problems. It can't use the year 2018 and it should use UNION again and again.
How can I make my SQL query more beautiful?

Answer 1

Try this
select
date_format(created_at,'%Y') as Year,
sum(case when date_format(created_at,'%m')='01' then 1 else 0 end) as val01,
sum(case when date_format(created_at,'%m')='02' then 1 else 0 end) as val02,
sum(case when date_format(created_at,'%m')='03' then 1 else 0 end) as val03,
sum(case when date_format(created_at,'%m')='04' then 1 else 0 end) as val04,
sum(case when date_format(created_at,'%m')='05' then 1 else 0 end) as val05,
sum(case when date_format(created_at,'%m')='06' then 1 else 0 end) as val06,
sum(case when date_format(created_at,'%m')='07' then 1 else 0 end) as val07,
sum(case when date_format(created_at,'%m')='08' then 1 else 0 end) as val08,
sum(case when date_format(created_at,'%m')='09' then 1 else 0 end) as val09,
sum(case when date_format(created_at,'%m')='10' then 1 else 0 end) as val10,
sum(case when date_format(created_at,'%m')='11' then 1 else 0 end) as val11,
sum(case when date_format(created_at,'%m')='12' then 1 else 0 end) as val12,
count(*) as total
from reservations
group by date_format(created_at,'%Y')

Answer 2

You can try with below query
SELECT YEAR,SUM(VAL01) VAL02,SUM(VAL02) VAL02,SUM(VAL03) VAL3
FROM
(
SELECT date_format(created_at,'%Y') YEAR,
CASE WHEN date_format(created_at,'%m')=1 THEN 1 ELSE 0 END AS VAL01,
CASE WHEN date_format(created_at,'%m')=2 THEN 1 ELSE 0 END AS VAL02,
CASE WHEN date_format(created_at,'%m')=3 THEN 1 ELSE 0 END AS VAL03
FROM reservations
)t
GROUP BY YEAR
Hope this will helps.

Answer 3

If this had been Oracle, you could have used Function based index on column Created_at and using the same function (EXTRACT in this case) in your query:
CREATE INDEX IDX1 ON RESERVATIONS (EXTRACT(YEAR FROM CREATED_AT))
Since, this is MySQL, try using this as alternative. Make sure after creating the index, it is getting used by verifying the Query plan.

Answer 4

You could try this query
SELECT id,
Year,
SUM(CASE WHEN Month='01' THEN MonthCount ELSE 0 END) AS 'VAL01',
SUM(CASE WHEN Month='02' THEN MonthCount ELSE 0 END) AS 'VAL02',
SUM(CASE WHEN Month='03' THEN MonthCount ELSE 0 END) AS 'VAL03',
SUM(CASE WHEN Month='04' THEN MonthCount ELSE 0 END) AS 'VAL04',
SUM(CASE WHEN Month='05' THEN MonthCount ELSE 0 END) AS 'VAL05',
SUM(CASE WHEN Month='06' THEN MonthCount ELSE 0 END) AS 'VAL06',
SUM(CASE WHEN Month='07' THEN MonthCount ELSE 0 END) AS 'VAL07',
SUM(CASE WHEN Month='08' THEN MonthCount ELSE 0 END) AS 'VAL08',
SUM(CASE WHEN Month='09' THEN MonthCount ELSE 0 END) AS 'VAL09',
SUM(CASE WHEN Month='10' THEN MonthCount ELSE 0 END) AS 'VAL10',
SUM(CASE WHEN Month='11' THEN MonthCount ELSE 0 END) AS 'VAL11',
SUM(CASE WHEN Month='12' THEN MonthCount ELSE 0 END) AS 'VAL12',
SUM(MonthCount) AS Total
FROM (
SELECT
CASE
WHEN Date_format(created_at, '%Y') = '2016' THEN 1
WHEN Date_format(created_at, '%Y') = '2017' THEN 2
WHEN Date_format(created_at, '%Y') = '2018' THEN 3
END AS id,
Date_format(created_at, '%Y') AS Year,
Date_format(created_at, '%m') AS Month,
COUNT(1) AS MonthCount
FROM reservations
WHERE Date_format(created_at, '%Y') IN ('2016', '2017', '2018')
GROUP BY Date_format(created_at, '%Y-%m')) AS ByMonth
GROUP BY id, Year