HAVING

The HAVING clause allows you to filter grouped (aggregated) results—it works like WHERE, but after grouping has taken place. The HAVING clause was added to SQL because the WHERE clause cannot be used with aggregate functions.

Examples

Find days where the average CPU utilization exceeded 80%:

SELECT
  date_trunc('day', ts) AS day,
  AVG(cpu_util) AS avg_cpu_util
FROM
  system_metrics
GROUP BY
  day
HAVING
  avg_cpu_util > 80;

Find hours where the number of error logs is greater than 100:

SELECT
  DATE_TRUNC('hour', log_time) AS hour,
  COUNT(*) AS error_count
FROM
  application_logs
WHERE
  log_level = 'ERROR'
GROUP BY
  hour
HAVING
  error_count > 100;