PIVOT
to není snadné (ani hezké). Preferuji použití CASE
:
SELECT d.data_timestamp
, SUM( CASE WHEN data_id = 1 THEN data_value ELSE 0 END ) AS 'input_1'
, SUM( CASE WHEN data_id = 2 THEN data_value ELSE 0 END ) AS 'input_2'
...
, SUM( CASE WHEN data_id = 20 THEN data_value ELSE 0 END ) AS 'input_20'
FROM data
GROUP BY data_timestamp
ORDER BY data_timestamp ASC
ale IF
funguje také v MySQL:
SELECT d.data_timestamp
, SUM( IF(data_id = 1, data_value, 0) ) AS 'input_1'
, SUM( IF(data_id = 2, data_value, 0) ) AS 'input_2'
...
, SUM( IF(data_id = 20, data_value, 0) ) AS 'input_20'
FROM data
GROUP BY data_timestamp
ORDER BY data_timestamp ASC
Případně můžete použít 20úrovňový JOIN
:
SELECT d.data_timestamp
, d01.data_value AS 'input_1'
, d02.data_value AS 'input_2'
...
, d20.data_value AS 'input_20'
FROM
( SELECT DISTINCT d.data_timestamp
FROM data
) AS d
LEFT JOIN data AS d01
ON d01.data_timestamp = d.data_timestamp
AND d01.data_id = 1
LEFT JOIN data AS d02
ON d02.data_timestamp = d.data_timestamp
AND d02.data_id = 2
... --- 20 JOINs
LEFT JOIN data AS d20
ON d20.data_timestamp = d.data_timestamp
AND d20.data_id = 20
ORDER BY d.data_timestamp ASC