Hi, @pailin
Thanks for your response! This is my new test flow:

(1)Compose 3 and Compose 4 are used to create test data:

(2)The initialize variable action:

(3)The "Apply to each 3 " action:

item()?['ID']
items('Apply_to_each_3')?['ID']
json( concat( '[' , string( items('Apply_to_each_3') ) , ']' ) )
item()?['Email']
body('Filter_array_2')?[0]?['Name']
body('Select_2')?[0]
(4) The Select action is the same as above:

(5)The "Apply to each 2" action:

union(body('Select'),body('Select'))
You may need to replace your action name in your side.
Best Regards,
Yueyun Zhang