How can I set to zero when query return null from mysql

qishiwenjun · August 18, 2020, 2:30am

my query like

SELECT
  timeField AS "time",
  count(field) AS "<= 3d"
FROM table
WHERE
  Condition1 AND
  Condition2

but it return null value, while grafana report that timestamp should not be empty. then it can not show graph.

chart: Pie Chart