list empty verification sql statement

[lfoIncluit]

How can I verify if list is empty in a rule statement. Example:

{ "sql": "SELECT at1,at2,at3 FROM stream1 WHERE at1 != [] AND at1[:]->subat1 != NULL", "actions": [ { "log": {} }, { "mqtt": { "server": "tcp://172.17.0.1:1883", "topic": "topic1" } } ] }

[ngjaying]

There is a cardinality function to check the length of a list: cardinality(at1) = 0. Please check the doc https://ekuiper.org/docs/en/latest/sqls/built-in_functions.html#other-functions