MariaDB 10.4

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CREATE TABLE table2 (id varchar(20), `timestamp` TIMESTAMP, detector11 DECIMAL(4,2), detector12 DECIMAL(4,2)
, detector21 DECIMAL(4,2), detector22 DECIMAL(4,2))
CREATE TABLE table1 (`timestamp`TIMESTAMP, value DECIMAL(4,2), unit INT,detector INT)
INSERT INTO table2
(id, timestamp, detector11, detector12, detector21, detector22)
SELECT UUID(),t1a.timestamp, t1a.detector11,t1b.detector12,t1c.detector21,t1d.detector22
FROM
(SELECT
t1.timestamp, t1.value as detector11 FROM table1 t1
WHERE t1.unit='1' AND t1.detector='1'
ORDER BY timestamp ) t1a
JOIN
	(SELECT t1.timestamp, t1.value AS detector12 FROM table1 t1
       WHERE t1.unit='1' AND t1.detector='2'
       ORDER BY timestamp) t1b
       ON t1a.timestamp = t1b.timestamp
JOIN       
	(SELECT t1.timestamp,t1.value AS detector21 FROM table1 t1
       WHERE t1.unit='2' AND t1.detector='1'
       ORDER BY timestamp) t1c
       ON t1a.timestamp = t1c.timestamp
JOIN
	(SELECT t1.timestamp,t1.value AS detector22 FROM table1 t1
       WHERE t1.unit='2' AND t1.detector='2'
       ORDER BY timestamp) t1d
	ON t1a.timestamp = t1d.timestamp

Records: 0  Duplicates: 0  Warnings: 0