sqlite - rails: How to find entries with empty arrays -

i've got issue finding empty arrays in sqlite table.

i serialized product_category param, works saving arrays db, follows:

serialize :product_category, array 

the following query find empty arrays param, giving me nil error:

product.where(product_category: []).first 

how find products product_category has no values in array?

i tried using {} instead of [] suggested in similar postgress related question.

does know right way?

i have tried on mysql, works me, please try.

#product.rb serialize :product_category, array  #rails console >> product = product.new >> product.product_category = [] >> product.save >> product.where("product_categoty = '[]'") #it returns last record have created. 

hope help!