如何连接日期并在日期月份下检索

Question

I am using holiday table as:

I want to retrive 1 row having columns Jan To Dec and data as all holidays in respective month. I tried with

SELECT 
(CASE WHEN MONTH(hd.holiday_date)=1 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as JAN, 
(CASE WHEN MONTH(hd.holiday_date)=2 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as FEB, 
(CASE WHEN MONTH(hd.holiday_date)=3 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as MAR, 
(CASE WHEN MONTH(hd.holiday_date)=4 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as APR, 
(CASE WHEN MONTH(hd.holiday_date)=5 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as MAY, 
(CASE WHEN MONTH(hd.holiday_date)=6 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as JUN, 
(CASE WHEN MONTH(hd.holiday_date)=7 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as JUL, 
(CASE WHEN MONTH(hd.holiday_date)=8 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as AUG, 
(CASE WHEN MONTH(hd.holiday_date)=9 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as SEP, 
(CASE WHEN MONTH(hd.holiday_date)=10 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as OCT, 
(CASE WHEN MONTH(hd.holiday_date)=11 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as NOV, 
(CASE WHEN MONTH(hd.holiday_date)=12 THEN GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) ELSE NULL END) as DECE
FROM `holiday` `hd`
WHERE `year` = '2020'
GROUP BY MONTH(hd.holiday_date)   

with group by getting result but multiple rows are returing as

without group by returning single row but not getting under proper month as

Please suggest me correct way. Thanks.

Answer 1

1) Create inner query where group them by months

SELECT
  MONTH(hd.holiday_date) as m, 
  GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) as name
FROM holiday as hd
GROUP BY MONTH(hd.holiday_date) 

2) In outer query do something like

SELECT 
  MAX(case when m = 1 then name else "" end) as Jan
  MAX(case when m = 2 then name else "" end) as Feb
FROM (inner)

So the result will be

SELECT 
  MAX(case when m = 1 then name else "" end) as Jan,
  MAX(case when m = 2 then name else "" end) as Feb
  // etc
FROM (
  SELECT
    MONTH(hd.holiday_date) as m, 
    GROUP_CONCAT(CONCAT(hd.holiday_date, '#', hd.holiday_name)) as name
  FROM holiday as hd
  GROUP BY MONTH(hd.holiday_date) 
) as grouped

Answer 2

I think it's the other way around:

SELECT GROUP_CONCAT(CASE WHEN MONTH(holiday_date)=3 
                         THEN CONCAT_WS('#',holiday_date,holiday_name) 
                         ELSE NULL END) AS 'March',
       GROUP_CONCAT(CASE WHEN MONTH(holiday_date)=4 
                         THEN CONCAT_WS('#',holiday_date,holiday_name) 
                         ELSE NULL END) AS 'April'
FROM   holiday
WHERE  YEAR=2020
GROUP  BY YEAR;

Fiddle example here: https://www.db-fiddle.com/f/2DUDuiGM4T12Ah7hxuPTdB/1