Mysql attendence report creates syntax error on prepare stmt - mysql

Question

I have two tables: One with just a list of dates called date_range (column name is Date) and one called wp_wpdatatable_1 in which all the date is stored (after each practice, a row for every player is created with the name of the player (player), date of practice (date), duration (sporttrainingduration), what practice group (practiceheldby) etc...
Now I want to create a report.
I want every day of the month across, the players names in the first column and on every day a player was at a practice I want to list which practice he attended (wp_wpdatatable_1.practiceheldby)
-- 1. Create an expression that builds the columns
set #sql = (
select group_concat(distinct
concat(
"max(case when date_range.`date`='", date_range.`Date`, "' then `practiceheldby` end) as `", date_range.`Date`, "`"
)
)
from wp_wpdatatable_1, date_range
where date_range.`Date`>=2019-06-01
and date_range.`Date` <= 2019-06-07
);
-- 2. Complete the SQL instruction
set #sql = concat("select `player`, ", #sql , " from wp_wpdatatable_1 group by `player`");
-- 3. Create a prepared statement
PREPARE stmt from #sql;
-- 4. Execute the prepared statement
execute stmt;
DEALLOCATE PREPARE stmt;
I'm not a pro and I've played with this for 3 or four days now. I think I'm very close, but I get this error message:
PREPARE stmt from #sql
MySQL meldet: Dokumentation
#1064 - Fehler in der SQL-Syntax. Bitte die korrekte Syntax im Handbuch nachschlagen bei 'NULL' in Zeile 1
What am I missing?
thank you!

Answer 1

You're very close. Besides the missing quotes on dates, the case when date_range.date should be case when date in line 5 of your code.
-- 0. Toy data
CREATE TABLE date_range (
`Date` datetime
);
CREATE TABLE wp_wpdatatable_1 (
`player` VARCHAR(5),
`Date` DATE,
`sporttrainingduration` FLOAT,
`practiceheldby` VARCHAR(10)
);
INSERT INTO date_range
VALUES
('2019-06-01'),
('2019-06-02'),
('2019-06-03')
;
INSERT INTO wp_wpdatatable_1
VALUES
('AAA','2019-06-01','1','group1'),
('AAA','2019-06-02','2','group2'),
('AAA','2019-06-03','3','group3'),
('AAA','2019-06-04','1','gorup1'),
('BBB','2019-06-02','2','group2'),
('CCC','2019-06-03','3','group3')
;
select * from date_range;
select * from wp_wpdatatable_1;
date_range
===================
Date
===================
2019-06-01 00:00:00
2019-06-02 00:00:00
2019-06-03 00:00:00
wp_wpdatatable_1
=======================================================
player Date sporttrainingduration practiceheldby
=======================================================
AAA 2019-06-01 1 group1
AAA 2019-06-02 2 group2
AAA 2019-06-03 3 group3
AAA 2019-06-04 1 gorup1
BBB 2019-06-02 2 group2
CCC 2019-06-03 3 group3
The updated code below:
-- 1. Create an expression that builds the columns
set #sql = (
select group_concat(distinct
concat(
-- "max(case when date_range.`date`='", date_range.`Date`, "' then `practiceheldby` end) as `", date_range.`Date`, "`"
"max(case when `date`='", date_range.`Date`, "' then `practiceheldby` end) as `", date_range.`Date`, "`"
)
)
from wp_wpdatatable_1, date_range
-- where date_range.`Date`>=2019-06-01
-- and date_range.`Date` <= 2019-06-07
where date_range.`Date`>='2019-06-01'
and date_range.`Date` <= '2019-06-07'
);
Output:
===========================================================================
player 2019-06-01 00:00:00 2019-06-02 00:00:00 2019-06-03 00:00:00
===========================================================================
AAA group1 group2 group3
BBB null group2 null
CCC null null group3
Code here