需求：从两个不同的结果集（一个是子集，一个是父集），字段为电话号码phone_number,找出父集中缺少的电话号码，以明确用户身份。
结合网上资料，整理sql如下：
//mysql取差集
select num FROM(select u.code_sn as id,u.phone_number as num from ng_cash_balance bleft join ng_user uon b.from_user=u.code_snwhere b.to_account='10030000000000011001' and b.json_info like '%员工09月份%'union allselect u.code_sn as id,u.phone_number as num from ng_order oleft join ng_user uon o.buyer_code_sn=u.code_snwhere o.seller_account_code_sn='10030000000000011001' and o.json_info like '%员工09月份%' )t3group by num having count(num)=1
//mysql取交集
select num FROM(select u.code_sn as id,u.phone_number as num from ng_cash_balance bleft join ng_user uon b.from_user=u.code_snwhere b.to_account='10030000000000011001' and b.json_info like '%员工09月份%'union allselect u.code_sn as id,u.phone_number as num from ng_order oleft join ng_user uon o.buyer_code_sn=u.code_snwhere o.seller_account_code_sn='10030000000000011001' and o.json_info like '%员工09月份%' )t3group by num having count(num)=2
//mysql取并集
select num FROM(select u.code_sn as id,u.phone_number as num from ng_cash_balance bleft join ng_user uon b.from_user=u.code_snwhere b.to_account='10030000000000011001' and b.json_info like '%员工09月份%'union allselect u.code_sn as id,u.phone_number as num from ng_order oleft join ng_user uon o.buyer_code_sn=u.code_snwhere o.seller_account_code_sn='10030000000000011001' and o.json_info like '%员工09月份%' )t3