MYSQL: conditional GROUP BY from parameter? - mysql

Question

Im trying to code a procedure that groups by a parameter variable, but at this time, its impossible for me. Its possible to do or i'm writting any mistake?
The finally of this procedure is retrieve a list of values, grouped by time periods Whitout the group by line, it works fine. (granularity its a procedure parameter)
SET g = CASE granularity
WHEN 'week' THEN 'WEEK(r.value_date,1),YEAR(r.value_date)'
WHEN 'month' THEN 'MONTH(r.value_date,1),YEAR(r.value_date)'
ELSE 'r.value_date'
END;
INSERT INTO system_temp_points_data (`method`,`value`,`num_rows`,value_date,ref,units_id,unit_name,`hash`,granularity) SELECT
'sum' AS `method`,
SUM(`value`) AS `value`,
COUNT(`value`) AS num_rows,
UNIX_TIMESTAMP(MIN(value_date)) AS value_date,
GROUP_CONCAT(raw_data_id) AS ref,
r.units_id,
u.unit_name,
aux_hash,
granularity
FROM
raw_data r
JOIN temp_unit_group t ON (r.units_id = t.units_id)
JOIN units u ON (t.units_id = u.units_id)
AND (t.start_date <= r.value_date)
AND (t.end_date >= r.value_date)
WHERE
r.value_date BETWEEN start_date
AND end_date
AND kpis_id = kpi
AND IF(exclude_zeros = 1,`value` <> '0',true)
AND IF(value_aux IS NOT NULL,r.aux = value_aux,true)
GROUP BY g
ORDER BY
r.value_date ASC;

Answer 1

The strings in g are not evaluated when it's used in the query. You need to put that condition in the query itself:
GROUP BY CASE granularity
WHEN 'week' THEN WEEK(r.value_date,1)
WHEN 'month' THEN MONTH(r.value_date)
ELSE r.value_date
END,
CASE granularity
WHEN 'week' THEN YEAR(r.value_date)
WHEN 'month' THEN YEAR(r.value_date)
ELSE 1
END
An alternative is to use a prepared statement, and merge g into it:
SET #sql = CONCAT("INSERT INTO system_temp_points_data (`method`,`value`,`num_rows`,value_date,ref,units_id,unit_name,`hash`,granularity) SELECT
'sum' AS `method`,
SUM(`value`) AS `value`,
COUNT(`value`) AS num_rows,
UNIX_TIMESTAMP(MIN(value_date)) AS value_date,
GROUP_CONCAT(raw_data_id) AS ref,
r.units_id,
u.unit_name,
aux_hash,
granularity
FROM
raw_data r
JOIN temp_unit_group t ON (r.units_id = t.units_id)
JOIN units u ON (t.units_id = u.units_id)
AND (t.start_date <= r.value_date)
AND (t.end_date >= r.value_date)
WHERE
r.value_date BETWEEN start_date
AND end_date
AND kpis_id = kpi
AND IF(exclude_zeros = 1,`value` <> '0',true)
AND IF(value_aux IS NOT NULL,r.aux = value_aux,true)
GROUP BY ", g, "
ORDER BY
r.value_date ASC";
PREPARE #stmt FROM #sql;
EXECUTE #stmt;