NULL value in：conditions =>

Question

Contract.all(:conditions => ['voided == ?', 0]).size 
=> 364 
Contract.all(:conditions => ['voided != ?', 0]).size 
=> 8 
Contract.all.size 
=> 441 

这3个数字没有加起来（364 + 8！= 441）。写入:conditions以计算voided列值为NULL或等于零的行的正确方法是什么？

Answer 1

Contract.all(:conditions => ["voided is ?", nil]).size 

Contract.all(:conditions => ["voided is not ?", nil]).size 

Answer 2

Contract.all(:conditions => {:voided => nil}) 

或

Contract.all(:conditions => ['voided IS NULL'])