¿Por qué no puedo usar alias de columna en la próxima expresión SELECT?
¿Puedo modificar el siguiente para usar los alias de columna?avg_time
ycnt
en una expresiónROUND(avg_time * cnt, 2)
?
SELECT
COALESCE(ROUND(stddev_samp(time), 2), 0) as stddev_time,
MAX(time) as max_time,
ROUND(AVG(time), 2) as avg_time,
MIN(time) as min_time,
COUNT(path) as cnt,
ROUND(avg_time * cnt, 2) as slowdown, path
FROM
loadtime
GROUP BY
path
ORDER BY
avg_time DESC
LIMIT 10;
Plantea el siguiente error:
ERROR: column "avg_time" does not exist
LINE 7: ROUND(avg_time * cnt, 2) as slowdown, path
El siguiente, sin embargo, funciona bien (use expresiones primarias en lugar de alias de columna:
SELECT
COALESCE(ROUND(stddev_samp(time), 2), 0) as stddev_time,
MAX(time) as max_time,
ROUND(AVG(time), 2) as avg_time,
MIN(time) as min_time,
COUNT(path) as cnt,
ROUND(AVG(time) * COUNT(path), 2) as slowdown, path
FROM
loadtime
GROUP BY
path
ORDER BY
avg_time DESC
LIMIT 10;