Нестандартное извлечение данных из БД

Например, так:

SELECT
MIN(IF(parameter = 't', value, NULL)) AS t_min,
MAX(IF(parameter = 't', value, NULL)) AS t_max,
AVG(IF(parameter = 't', value, NULL)) AS t_avg,
MIN(IF(parameter = 'p', value, NULL)) AS p_min,
MAX(IF(parameter = 'p', value, NULL)) AS p_max,
AVG(IF(parameter = 'p', value, NULL)) AS p_avg,
MIN(IF(parameter = 'h', value, NULL)) AS h_min,
MAX(IF(parameter = 'h', value, NULL)) AS h_max,
AVG(IF(parameter = 'h', value, NULL)) AS h_avg
FROM info
WHERE dt_created > NOW() - INTERVAL 1 MINUTE;

Или так:

SELECT * FROM
(SELECT MIN(value) AS t_min, MAX(value) AS t_max, AVG(value) AS t_avg
FROM info
WHERE parameter = 't' AND dt_created > NOW() - INTERVAL 1 MINUTE) AS t,
(SELECT MIN(value) AS p_min, MAX(value) AS p_max, AVG(value) AS p_avg
FROM info
WHERE parameter = 'p' AND dt_created > NOW() - INTERVAL 1 MINUTE) AS p,
(SELECT MIN(value) AS h_min, MAX(value) AS h_max, AVG(value) AS h_avg
FROM info
WHERE parameter = 'h' AND dt_created > NOW() - INTERVAL 1 MINUTE) AS h;

Или совершенно стандартным запросом, возвращающим 3 строки данных:

SELECT parameter, MIN(value) AS mn, MAX(value) AS mx, AVG(value) AS av
FROM info
WHERE dt_created > NOW() - INTERVAL 1 MINUTE
GROUP BY parameter;